Method and apparatus for producing dry particles

ABSTRACT

Method and apparatus for producing dry particles. Two liquid components are combined in a static mixer, atomized into droplets, and the droplets dried to form dry particles. Use of the static mixer enables incompatible liquid components to be rapidly and homogeneously combined. The present invention optimizes process conditions for increasing and controlling particle porosity. The present invention also allows for optimization of particle size in real-time during particle production.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/391,199, filed Mar. 19, 2003, which is a continuation-in-part of U.S.patent application Ser. No. 10/101,563, filed Mar. 20, 2002, each ofwhich is hereby incorporated in its entirety in this patent application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for producingdry particles. More particularly, the present invention relates to amethod and apparatus for producing dry particles that are suitable forinhalation into the lung, and which contain an active agent.

2. Related Art

Delivery of drugs and other active agents can be accomplished throughthe use of dry powder compositions made from particles containing thedrug or active agent. In producing such particles, it is often desirableto combine substances with significantly different physical propertiesto achieve the desired pharmaceutical effect in patients. Moreover, itis often desirable to produce particles that are a combination ofdifferent substances. One way to produce particles containing acombination of different substances is to dissolve the substances insuitable solvents, and then remove the solvents by, for example,evaporation or drying, to yield the desired particles. A majordifficulty with this approach is that substances with differing physicalproperties often have very different solubilities in solvents.Consequently, co-solvents, or a larger mixture of solvents, may beneeded to form the solution from which the particles are produced.However, the use of co-solvents can cause degradation of one of thecomponents, through chemical or physical incompatibility of thecomponents in solution.

One example of the incompatibility of components is the production ofparticles that contain a hydrophobic component and a hydrophiliccomponent. The production of such particles is described in U.S. Pat.No. 6,077,543 to Gordon et al. (“the Gordon patent”). As described inthe Gordon patent, a hydrophobic drug solution and a hydrophilicexcipient solution are spray dried together to form dry powderscontaining the drug and the excipient. To solve the incompatibilitybetween the hydrophobic and hydrophilic components, the hydrophilic andhydrophobic components are separately dissolved in different solvents,and separately directed simultaneously through a nozzle into a spraydryer. In this method, the two liquid components are separatelydelivered to the nozzle that atomizes the two liquid components intodroplets that are dried in a spray dryer to form dry particles.

One of the drawbacks of the method and apparatus of the Gordon patent isthat there is no complete mixing of the two liquid components beforebeing atomized into droplets. Thus, the droplets that are produced areunlikely to be a homogeneous mixture of the two liquid components, noris there likely to be uniformity among the droplets. Consequently, theparticles that are produced are unlikely to contain a homogeneousmixture of the drug and excipients, and are unlikely to have uniformityamong the particles themselves. Thus, there is a need in the art for animproved method and apparatus for producing dry particles that contain ahomogenous mixture of drug and excipient components, with improveduniformity among the particles. There is a particular need in the artfor such a method and apparatus where the drug component and excipientcomponent are physically or chemically incompatible in the liquid state.

One important application for dry powder compositions is pulmonary drugdelivery. Several properties of the dry particles have been identifiedthat correlate with enhanced delivery to the pulmonary system. Forexample, it has been found that particles having a tap density less than0.4 g/cm³ and an aerodynamic diameter that is between about 1 and about3 microns (μm) are well suited for delivery to the alveoli or the deeplung. If delivery to the central or upper airways is desired, particleshaving larger aerodynamic diameters, ranging for example, from about 3to about 5 microns are preferred. Furthermore, particles having ageometric diameter greater than about 5 microns are believed to moresuccessfully avoid phagocytic engulfment by alveolar macrophages andclearance from the lungs.

There is a need in the art for improved methods for producing particleshaving selected geometric and aerodynamic sizes optimized for deliveryto targeted sites of the pulmonary system. There is a particular needfor an apparatus and method that allows for optimization of particlesize in real-time, during the particle production process.

The apparatus and method of the present invention, a description ofwhich is fully set forth below, solve the aforementioned problems anddifficulties with conventional approaches to producing dry powdercompositions.

SUMMARY OF THE INVENTION

The present invention is directed to a method and apparatus forproducing dry particles. The dry particles are advantageously formedinto dry powder compositions that can be administered to a patient, suchas a human patient, for therapeutic purposes. In a preferred aspect ofthe present invention, the dry powder compositions are formulated forinhalation by a patient for delivery of an active agent through thepulmonary system.

In one aspect of the present invention, a method for preparing a drypowder composition is provided. An embodiment of the method of thepresent invention comprises combining a first fluid component and asecond fluid component in a mixer to form a mixed fluid, wherein thefirst fluid component comprises an active agent that is incompatiblewith the second fluid component, atomizing the mixed fluid to producedroplets, and drying the droplets to form dry particles. In someembodiments, the first fluid component is hydrophilic and the secondfluid component is hydrophobic and the combining step comprises addingthe first fluid component to the second fluid component. In otherembodiments, the second fluid component is an organic solutioncomprising approximately 60-70% water by volume, and the mixed fluidcomprises approximately 20% organic phase by volume. In yet otherembodiments, the method produces dry particles with less than about 6%,and preferably less than about 3%, high molecular weight protein(“HMWP”) and more than about 90% readily extractable protein product(“RE”).

In alternative embodiments of the method of the present invention, themethod comprises atomizing the mixed fluid with an internal mixingnozzle, e.g., a single-hole nozzle or a six-hole nozzle. In otherembodiments, other types of nozzles may be used.

In some embodiments of the method of the present invention, the methodfurther comprises adding a surfactant, for example, a non-ionicsurfactant or DPPC or Tween 80, to the first fluid component, the secondfluid component, or the mixed fluid. In some embodiments, at least 0.2wt % of Tween 80 is added. In other embodiments, 0.2-2.8 wt % of Tween80 is added.

In yet other embodiments of the method of the present invention, themethod comprises using a total solids concentration for the mixed fluidof about 1-60 g/L.

In yet other embodiments of the method of the present invention, themethod comprises adding about 5-40 g/L ammonium bicarbonate to the firstfluid component, the second fluid component, or the mixed fluid.

In another embodiment of the method of the present invention, the methodcomprises performing the drying step in a dryer with an outlettemperature of 35-70° C. In alternative embodiments, a drying gas rateof approximately 80-125 kg/hr is used.

Alternative embodiments of the method of the present invention compriseascertaining the amount of solid and liquid ingredients necessary toachieve the first solution concentration and combining the liquid andsolid ingredients together to form the first fluid component.

In yet other alternative embodiments of the method of the presentinvention, the method comprises using an atomization gas rate ofapproximately 35-120 g/min.

In other embodiments of the method of the present invention, the methodcomprises using a liquid feed rate of approximately 10-75 mL/min duringthe atomization step.

In an aspect of the apparatus of the present invention, an apparatus forpreparing a dry powder composition is provided. An embodiment of theapparatus of the present invention comprises a static mixer operative tocombine a first fluid component with a second fluid component to form amixed fluid, wherein the first fluid component comprises an active agentthat is incompatible with the second fluid component. The apparatusfurther comprises an atomizer in fluid communication with the staticmixer, whereby the mixed fluid is atomized to form droplets, and a dryerwherein the droplets are dried to form dry particles. In someembodiments of the apparatus of the present invention, the atomizercomprises an internal mixing nozzle, e.g., a single-hole nozzle or asix-hole nozzle. In other aspects of the invention, a sheeting actionnozzle or a pressure nozzle may also be used.

In yet another aspect of the present invention, a method for preparing adry powder composition is provided. In such a method, a hydrophiliccomponent and a hydrophobic component are prepared, one of whichcomprises an active agent. The hydrophobic and hydrophilic componentsare combined in a static mixer to form a combination. The combination isatomized to produce droplets, which are dried to form dry particles. Ina preferred aspect of this method, the atomizing step is performedimmediately after the components are combined in the static mixer. Inanother preferred aspect of this method, the hydrophilic componentcomprises an active agent that may include, for example, insulin,albuterol sulfate, L-DOPA, humanized monoclonal antibody (for example,IgG1), human growth hormone (hGH), epinephrine, and ipatropium bromidemonohydrate.

In a further aspect of the present invention, a method for preparing adry powder composition is provided. In such a method, first and secondcomponents are prepared, one of which comprises an active agent. Thefirst and second components are combined in a static mixer to form acombination. The first and second components are such that combiningthem causes degradation in one of the components. In a preferred aspect,the active agent is incompatible with the other component. Thecombination is atomized to produce droplets that are dried to form dryparticles. In a preferred aspect of such a method, the first componentcomprises an active agent dissolved in an aqueous solvent, and thesecond component comprises an excipient dissolved in an organic solvent.

In yet a further aspect of the present invention, a method for preparinga dry powder composition is provided. In such a method, a first phase isprepared that comprises human growth hormone, sodium phosphate, andammonium bicarbonate. A second phase is prepared that comprises ethanol.The first and second phases are combined in a static mixer to form acombination. The combination is atomized to produce droplets that aredried to form dry particles. In another aspect of such a method, thesecond phase further comprises1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC). In a furtheraspect of such a method, the resulting dry particles consist essentiallyof about 93% human growth hormone and about 7% sodium phosphate byweight of total human growth hormone and sodium phosphate. In still afurther aspect of such a method, the resulting particles consistessentially of about 79% human growth hormone, about 7% sodiumphosphate, and about 14% DPPC by weight of total human growth hormone,sodium phosphate, and DPPC.

In still a further aspect of the present invention, a method forpreparing a dry powder composition is provided. In such a method, ahydrophilic component is combined with an organic solvent in a staticmixer to form a combination. The combination is atomized to producedroplets that are dried to form dry particles. In a preferred aspect ofsuch a method, the hydrophilic component comprises an active agent. In afurther aspect of such a method, the hydrophilic component furthercomprises an excipient.

In yet a further aspect of the present invention, an apparatus forpreparing a dry powder composition is provided. The apparatus includes astatic mixer having an inlet end and an outlet end. The static mixer isoperative to combine an aqueous component with an organic component toform a combination. Means are provided for transporting the aqueouscomponent and the organic component to the inlet end of the staticmixer. An atomizer is in fluid communication with the outlet end of thestatic mixer to atomize the combination into droplets. The droplets aredried in a dryer to form dry particles. In one aspect of the presentinvention, the atomizer is a rotary atomizer. Such a rotary atomizer maybe vaneless, or may contain a plurality of vanes. In a further aspect ofthe present invention, the atomizer is a two-fluid mixing nozzle. Such atwo-fluid mixing nozzle may be an internal mixing nozzle or an externalmixing nozzle. In one aspect of the present invention, the means fortransporting the aqueous and organic components are two separate pumps.Alternatively, a single pump could be used. In a further aspect, theapparatus also includes a geometric particle sizer that determines ageometric diameter of the dry particles, and an aerodynamic particlesizer that determines an aerodynamic diameter of the dry particles.

In still a further aspect of the present invention, a method forpreparing dry particles having a selected volume median geometricdiameter is provided. Such a method comprises:

-   -   drying atomized liquid droplets to form dry particles;    -   selecting a particle density (ρ);    -   measuring a measured mass median aerodynamic diameter (d_(a)        ^(m)) of the dry particles;    -   measuring a measured volume median geometric diameter (d_(g)        ^(m)) of the dry particles;    -   calculating a calculated volume median geometric diameter (d_(g)        ^(c)) from the particle density and the measured mass median        aerodynamic diameter from the equation d_(a) ^(m)=d_(g)        ^(c)√{square root over (ρ)}; and    -   adjusting the particle density until the calculated volume        median geometric diameter is substantially equal to the measured        volume median geometric diameter.

In another aspect of such a method, the adjusting-step comprises:

-   -   comparing the calculated volume median geometric diameter to the        measured volume median geometric diameter to determine a        differential; and    -   responsive to the differential, changing a particle density        value in an aerodynamic particle sizer.

In still another aspect of such a method, a liquid feed is atomized toform the atomized liquid droplets. In a preferred aspect, a first liquidcomponent and a second liquid component are combined in a static mixerto form the liquid feed.

In yet a further aspect of the present invention, a system for preparingdry particles having a selected geometric diameter is provided. Thesystem includes a dryer that dries liquid droplets to form dryparticles. The system also includes a geometric particle sizer coupledto the dryer that determines a measured geometric diameter (d_(g) ^(m))of the dry particles. The system also includes an aerodynamic particlesizer coupled to the dryer that determines a measured aerodynamicdiameter (d_(a) ^(m)) of the dry particles responsive to a density (ρ)of the dry particles. A further component of the system is a processorcoupled to the aerodynamic particle sizer. The processor is responsiveto a program configured for calculating a calculated geometric diameter(d_(g) ^(c)) from the density and the measured aerodynamic diameter fromthe equation d_(a) ^(m)=d_(g) ^(c) √{square root over (ρ)}, andadjusting the density until the calculated geometric diameter issubstantially equal to the measured geometric diameter. In a furtheraspect of such a system, the program is configured to carry out theadjusting by comparing the calculated geometric diameter to the measuredgeometric diameter to determine a differential, and, responsive to thedifferential, changing the density used by the aerodynamic particlesizer. In a further aspect of such a system, an atomizer is coupled tothe dryer to atomize a liquid feed to form the liquid droplets. In stilla further aspect of such a system, a static mixer is in fluidcommunication with the atomizer, the static mixer combining a firstliquid component and a second liquid component to form the liquid feed.

Features and Advantages

It is a feature of the present invention that a static mixer is used tocombine two liquid components to form a combination that is atomizedinto droplets that are dried to form particles. The static mixeradvantageously provides rapid and homogeneous mixing of the two liquidcomponents. This is particularly advantageous when the two liquidcomponents are physically and/or chemically incompatible with eachother. Because of the homogeneous mixing provided by the static mixer,the particles resulting from use of the apparatus and method of thepresent invention advantageously have substantially the same compositionat the particle scale. A mixer other than a static mixer may be used toachieve similar results. When the two liquid components are physicallyand/or chemically incompatible with each other, the mixture should beremoved from the nonstatic mixer as quickly as possible in order tominimize degradation of product and then immediately atomized.

It is a further feature of the present invention that the liquid feedsolution to be atomized is fully mixed prior to atomization. The presentinvention also advantageously minimizes the time that the liquid feedsolution to be atomized remains in its combined state prior toatomization.

Another feature of the present invention is that it can be used toproduce particles that contain a hydrophilic active agent, andhydrophilic or hydrophobic excipients.

Another feature of the present invention is that it can be used toproduce dry particles that are particularly well adapted for inhalationinto the lung, particularly the deep lung. As one example, the presentinvention advantageously optimizes process conditions for increasing andcontrolling particle porosity. As another example, the formulations ofthe present invention advantageously include ammonium bicarbonate thatincreases particle porosity. As yet another example, the presentinvention provides a method and apparatus that can be used to optimizeparticle size in real-time during the particle production process. Inthis manner, process conditions for particles of selected geometricand/or aerodynamic size can advantageously be optimized using a minimalamount of material.

BRIEF DESCRIPTION OF THE FIGURES

The present invention is described with reference to the accompanyingdrawings. In the drawings, like reference numbers indicate identical orfunctionally similar elements. The left most digit(s) of a referencenumber indicates the figure in which the reference number first appears.

FIG. 1A illustrates flow through a static mixer

FIG. 1B shows a static mixer suitable for use with the presentinvention;

FIG. 2 illustrates one embodiment of a system of the present inventionfor producing dry particles;

FIG. 3 shows a vaned rotary atomizer suitable for use with the presentinvention;

FIG. 4A illustrates one embodiment of an internal mixing nozzle suitablefor use with the present invention;

FIG. 4B illustrates another embodiment of an internal mixing nozzlesuitable for use with the present invention;

FIG. 4C illustrates yet another embodiment of an internal mixing nozzlesuitable for use with the present invention;

FIG. 4D illustrates still another embodiment of an internal mixingnozzle suitable for use with the present invention;

FIG. 4E illustrates another embodiment of a nozzle suitable for use withthe present invention;

FIG. 5 illustrates one embodiment of an external mixing nozzle suitablefor use with the present invention;

FIG. 6 illustrates an alternate embodiment of a system of the presentinvention for producing dry particles;

FIG. 7 shows a flow chart of one embodiment of a process of the presentinvention for optimizing particle size;

FIG. 8 illustrates one embodiment of a computer system suitable for usewith the present invention;

FIG. 9 shows a graph of mass median aerodynamic diameter (MMAD) asmeasured using the system and method of the present invention versusMMAD measured using a multi-stage liquid impinger (MSLI); and

FIG. 10. shows a graph that illustrates the effect of the order ofaddition on soluble aggregate (dimer) levels as a function of ethanolconcentration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Overview

The present invention is directed to apparatus and methods for preparingdry particles.

The present invention has particular applicability for preparing dryparticles, and dry powder compositions, for inhalation into the lung fortherapeutic purposes. Particularly, preferred dry particles includethose described and disclosed in the following eleven applications:“Inhalable Sustained Therapeutic Formulations,” Appl. No. 60/366,479(filed Mar. 20, 2002); “Inhalable Salmeterol and IpratropiumCompositions,” Appl. No. 60/366,449 (filed Mar. 20, 2002); “InhalableSalmeterol and Ipratropium Compositions,” Appl. No. 60/366,354 (filedMar. 20, 2002); “Inhalable Salmeterol and Ipratropium Compositions,”Appl. No. 60/366,470 (filed Mar. 20, 2002); “Inhalable Salmeterol andIpratropium Compositions,” Appl. No. 60/366,487 (filed Mar. 20, 2002);“Inhalable Salmeterol and Ipratropium Compositions,” Appl. No.60/366,440 (filed Mar. 20, 2002); “hGH (Human Growth Hormone)Formulations for Pulmonary Administration,” Appl. No. 60/366,488 (filedMar. 20, 2002); “Pulmonary Delivery for LevoDOPA,” Appl. No. 60/366,471(filed Mar. 20, 2002); “Inhalable Sustained Therapeutic Formulations,”Appl. No. ______, Attorney Docket No. 2685.2034-001 US (filed Mar. 19,2003); “hGH (Human Growth Hormone) Formulations for PulmonaryAdministration,” Appl. No. ______, Attorney Docket No. 2685.2040-001 US(filed Mar. 19, 2003); and “Pulmonary Delivery for LevoDOPA,” Appl. No.______, Attorney Docket No. 2685.2044-001 US (filed Mar. 19, 2003), theentirety of each of which is incorporated herein by reference. Thedescription that follows will provide examples of preparing such dryparticles. However, it should be understood by one skilled in the artthat the present invention is not limited to preparing dry particles, ordry powder compositions, suitable for inhalation into the lung, and thatdry particles for other purposes can be prepared. As used herein, theterm “dry” refers to particles that have a moisture and/or residualsolvent content such that the powder is physically and chemically stablein storage at room temperature, and is readily dispersible in aninhalation device to form an aerosol. The moisture and residual solventcontent of the particles can be below 10 wt %, can be below 7 wt %, orcan be lower.

The present invention solves the problems associated with preparing dryparticles that contain incompatible components by providing a method andapparatus that ensures a homogeneous mixture of the components in thefinished dry particle product, and improves uniformity among theparticles themselves. As used herein, “incompatible components” refersto components that may be chemically or physically incompatible witheach other when in contact. One example of incompatible components is aprotein in aqueous solution in which the protein is stable, and anorganic solution containing hydrophobic substances. The aqueous proteinsolution is incompatible with the hydrophobic organic solution since theorganic solution will cause degradation of the protein. In the method ofthe present invention, the incompatible components, such as ahydrophilic component and a hydrophobic component, are prepared andmaintained separately from each other until just prior to the particleproduction process. The term “hydrophobic component” refers to materialsthat are insoluble or sparingly or poorly soluble in water. Suchcompositions typically have a solubility below 5 mg/ml, usually below 1mg/ml, in water. The term “hydrophilic component” refers to materialsthat are highly soluble in water. Typical aqueous solubilities ofhydrophilic components will be greater than 5 mg/ml, usually greaterthan 50 mg/ml, and can be greater than 100 mg/ml. The incompatiblehydrophobic and hydrophilic components are combined in a static mixer toform a combination that is a homogeneous mixture of the incompatiblecomponents. Immediately thereafter, the combination is atomized intodroplets that are dried to form the dry particles. Through the use ofthe static mixer, the incompatible components can be very rapidlycombined into a homogeneous mixture. The use of the static mixersignificantly reduces the amount of time the incompatible components arein contact with each other, thereby minimizing or eliminating thedegradation effects resulting from such contact. The use of the staticmixer also ensures a complete mixing of the incompatible componentsbefore atomization so that each droplet, and thus each finished dryparticle, has substantially the same composition. Uniformity in thecomposition of the particles at the particle scale is a significantfactor in the efficacy of the dry particles when used for therapeuticpurposes.

When preparing dry particles and dry powder compositions for inhalation,it is desirable to increase the porosity of the particles so that theparticles can be inhaled into the lung, preferably into the deep lung.The present invention advantageously optimizes process conditions forincreasing and controlling particle porosity. In a preferred embodimentof the present invention, an internal mixing two-fluid nozzle is used toatomize a liquid feed stream to form atomized droplets. In an internalmixing two-fluid nozzle, one or more gas streams impinge upon a liquidfeed stream to atomize the liquid feed stream into atomized dropletsthat exit the nozzle. Such a nozzle allows for intimate contact betweenthe gas (such as nitrogen) and the liquid feed stream. This increasesthe amount of gas in the liquid feed stream and the resulting droplets.When the droplets are dried, the exiting gas contributes to the porosityof the finished dry particles. Increased gas in the droplets can also beachieved through the use of ammonium bicarbonate, or other volatilesalts, in the liquid feed stream. In alternative embodiments of thepresent invention, a variety of nozzle types may be used, including butnot limited to a single-hole nozzle, a six-hole nozzle, and a pressurenozzle.

If dry particles are being produced for inhalation into the lung, thenit is important to control the size of the particles during theproduction process. The particles can be characterized by aerodynamicdiameter (d_(a)) and geometric diameter (d_(g)). Aerodynamic diametercan be determined using a “time-of-flight” measurement system thataccelerates the particles being measured past two points. The time oftravel is measured, and correlated to an aerodynamic size through thefollowing relationship: d_(a)=d_(g) √{square root over (ρ)}, where ρ isthe density of the particles. A suitable device for determiningaerodynamic diameter is an aerodynamic particle sizer, such as the APSModel 3321, available from TSI, Inc., St. Paul, Minn. Such a devicemeasures the mass median aerodynamic diameter (MMAD) of the particles,as well as complete particle size distributions (PSD).

Laser diffraction techniques can be used to determine particle geometricdiameter. One such device is the Insitec online particle sizer,available from Malvern Instruments Ltd. The Insitec device consists ofan optical sensor head, a signal processing unit, and a computer forinstrument control and data collection and analysis. The Insitec devicemeasures volume median geometric diameter (VMGD) of the particles inreal-time as they are produced. In addition to VMGD, the Insitec devicegenerates complete particle size distributions (PSD), which allows anoperator to visually determine the polydispersity of the particles beinggenerated.

Through the apparatus and method of the present invention, optimizationof particle size is accomplished in real-time during particleproduction. In the process of the present invention, the density (ρ) ofthe particles is used as an optimization variable. The density of theparticles is adjusted until the measured geometric diameter is equal tothe geometric diameter calculated from the equation d_(a)=d_(g) √{squareroot over (ρ)}. One significant advantage of this method is that theliquid stream to be atomized and dried into particles needs to besprayed for only about three minutes to collect sufficient data tooptimize the process variables. This allows for the rapid screening ofmultiple process conditions using a minimal amount of material.Moreover, the total length of spraying time and material required issignificantly reduced.

The size distribution of airborne particles can be measured throughgravimetric analysis through the use of, for example, an AndersenCascade Impactor (ACI), Anderson Instruments, Smyrna, Ga. The ACI is amulti-stage device that separates aerosols into distinct fractions basedon aerodynamic size. The size cutoffs of each stage are dependent uponthe flow rate at which the ACI is operated. For the examples anddiscussion herein, a flow rate of 60 L/min is used, unless indicatedotherwise.

At each stage of the ACI, an aerosol stream passes through a series ofnozzles, and impinges upon an impaction plate. Particles with sufficientinertia impact the plate, while those with insufficient inertia toimpact the plate remain in the aerosol stream, and are carried to thenext stage. Each successive stage has a higher aerosol velocity in thenozzle so that smaller diameter particles are collected at eachsuccessive stage. Particles too small to be collected on the last stageare collected on a collection filter.

A two-stage ACI (ACI-2) is particularly advantageous for characterizingand optimizing dry particles for inhalation. The first fraction isreferred to as “FPF(5.6)”, or Fine Particle Fraction (5.6). Thisfraction corresponds to the percentage of particles having anaerodynamic diameter of less than 5.6 μm. The fraction of the particlesthat passes this stage and is deposited on the collection filter isreferred to as “FPF(3.4)”, or Fine Particle Fraction (3.4). Thisfraction corresponds to the percentage of particles having anaerodynamic diameter of less than 3.4 μm. FPF(5.6) has been demonstratedto correlate to the fraction of the dry particles that is capable ofinhalation into the lung of a patient. FPF(3.4) has been demonstrated tocorrelate to that fraction that is capable of reaching the deep lung ofa patient. The foregoing correlations provide a quantitative indicatorthat can be used with the process of the present invention to optimizethe production process and the resulting finished dry particles forinhalation into the lung.

In a further embodiment, a three-stage ACI (ACI-3) is used for particlecharacterization and optimization. The ACI-3 consists of only the topthree stages of the eight-stage ACI and allows for the collection ofthree separate powder fractions. For example, the ACI-3 configurationcan consist of 20 μm pore (stages −1 and 1) and 150 μm pore (stage 2)stainless steel screens which can be saturated with methanol. Thefraction of the powder that passes the final stage of ACI-3 is referredto as FPF(3.3)

Apparatus and Methods of the Present Invention

The apparatus and methods of the present invention will now be describedwith reference to the accompanying figures. As will be described belowin more detail with respect to FIG. 2, a static mixer is used to combinetwo liquid components to form a combination. The combination is atomizedto produce droplets that are dried to form dry particles. In oneembodiment of the present invention, the two liquid components are ahydrophilic component and a hydrophobic component. In anotherembodiment, the two components are such that combining the two causesdegradation in one of the components. In yet another embodiment, onecomponent is a hydrophilic component and the other component is anorganic solvent.

Static or motionless mixers consist of a conduit or tube in which isreceived a number of static mixing elements. Static mixers provideuniform mixing in a relatively short length of conduit, and in arelatively short period of time. With static mixers, the fluid movesthrough the mixer, rather than some part of the mixer, such as a blade,moving through the fluid. Flow through one embodiment of a static mixeris illustrated in FIG. 1A. A pump (not shown) introduces a stream of oneor more fluids into an inlet end of a static mixer 10 as shown generallyat 1. The stream is split and forced to opposite outside walls as showngenerally at 2. A vortex is created axial to the centerline of staticmixer 10, as shown generally at 3. The vortex is sheared and the processrecurs, but with the opposite rotation, as shown generally at 4. Theclockwise/counter-clockwise motion ensures a homogeneous product thatexits an outlet end of static mixer 10.

One embodiment of a static mixer is shown in FIG. 1B. Static mixer 10includes a number of stationary or static mixing elements 14 arranged ina series within a conduit or pipe 12. The number of elements can rangefrom, for example, 4 to 32 or more. Conduit 12 is circular incross-section and open at opposite ends for introducing (inlet end 18)and withdrawing (outlet end 16) fluids. Mixing element 14 comprisessegments 142. Each segment 142 consists of a plurality of generally flatplates or vanes 144. The two substantially identical segments 142 arepreferably axially staggered with respect to each other. A static mixeras shown in FIG. 1B is more fully described in U.S. Pat. No. 4,511,258,the entirety of which is incorporated herein by reference.

Turning now to FIG. 2, one embodiment of a system of the presentinvention for producing dry particles is shown. The system includes afirst feed vessel 210 and a second feed vessel 220. As will be explainedin more detail below with respect to the various examples, feed vessel210 can contain, for example, a hydrophilic component, an aqueoussolution, or other suitable liquid component. Feed vessel 220 cancontain, for example, a hydrophobic component, an organic solution, orother suitable liquid component. The contents of feed vessel 210 andfeed vessel 220 are transported, via suitable means, to an inlet end ofa static mixer 230. In one embodiment of the present invention, themeans for transporting is a first pump 212 for the contents of feedvessel 210, and a second pump 222 for the contents of feed vessel 220.Alternatively, a single pump could be used to transport the contents offeed vessels 210 and 220 to the inlet end of static mixer 230. As wouldbe readily apparent to one skilled in the art, other means fortransporting the contents of feed vessels 210 and 220 could be used. Inone embodiment of the present invention, feed vessels 210 and 220contain the same volume of liquid, and pumps 212 and 222 are operated atsubstantially the same rate. In other embodiments, pumps 212 and 222 areoperated at different rates. Pumps 212 and 222 may be gear pumps, orother types of pumps as would be apparent to one skilled in the art.

The contents of feed vessels 210 and 220 are combined in static mixer230 to form a combination. The combination is a homogeneous mixture ofthe liquid components entering the inlet end of static mixer 230. Asillustrated in FIG. 2, static mixer 230 may be oriented in a horizontalconfiguration, i.e., a central axis of static mixer 230 is perpendicularto a central axis of a spray dryer 250. Preferably, static mixer 230 isoriented in a vertical configuration, as shown, for example, in FIG. 6(discussed in more detail below). Static mixers suitable for use withthe present invention are illustrated in FIGS. 1A and 1B, and includemodel 1/4-21 made by Koflo Corporation and the ISG (Interfacial SurfaceGenerator) Mixer (Catalog #S01-012) made by Ross Engineering, Inc.,Savannah, Ga. The ISG Mixer comprises mixing elements enclosed in a pipehousing and shaped so that adjacent elements form a tetrahedral chamber.Holes through the elements provide the flow path.

An outlet end of static mixer 230 is in fluid communication with anatomizer 240. Atomizer 240 atomizes the combination flowing out ofstatic mixer 230 into droplets. Because the combination flowing out ofstatic mixer 230 is a homogeneous mixture of the input liquidcomponents, the droplets formed by atomizer 240 will also contain ahomogeneous mixture of the input liquid components. Atomizers suitablefor use with the present invention include, but are not limited to,rotary atomizers, two-fluid mixing nozzles, and pressure, ultrasonic,vibrating plate, and electrostatic nozzles, and combinations of theforegoing. Atomizers suitable for use with the present invention will bedescribed in more detail below with respect to FIGS. 3-5.

In a preferred embodiment of the present invention, the combinationformed in static mixer 230 is atomized immediately after the combinationis formed. That is, the outflow of static mixer 230 flows into atomizer240 for atomization. This is particularly advantageous when first feedvessel 210 and second feed vessel 220 contain incompatible componentssince the contact between the incompatible components will be minimized.

The droplets formed by atomizer 240 are dried in spray dryer 250 to formdry particles. Because the droplets formed by atomizer 240 contain ahomogeneous mixture of the input liquid components, the dry particlesformed by spray dryer 250 will also contain a homogeneous mixture of theinput liquid components. Spray dryers suitable for use with the presentinvention include a Mobile Minor, EX Model manufactured by Niro,Columbia, Md. Other commercially available spray dryers from supplierssuch as Niro, APV Systems, Denmark (e.g., the APV Anhydro Model), andSwenson, Harvey, Ill., also can be employed, as can scaled-up spraydryers suitable for industrial capacity production lines.

A drying gas is used in spray dryer 250 to dry the droplets to formdried particles. Examples of gases suitable for use with the presentinvention include, but are not limited to, air, nitrogen, argon, carbondioxide, helium, and combinations or mixtures thereof. In a preferredembodiment, nitrogen gas is used. As illustrated in FIG. 2, a nitrogengas supply 252 is coupled to spray dryer 250, through suitable valvesand regulators as would be apparent to one skilled in the art.

A bag house 260 is coupled to an outlet end 254 of spray dryer 250.Disposed within bag house 260 is a bag filter 262. A gas-solid stream,made up of the drying gas and the dry particles, exits outlet end 254.Exhaust lines 266 provide exhaust for spray dryer 250 and bag house 260.The gas-solid stream exiting spray dryer 250 enters bag house 260. Bagfilter 262 retains the dry particles, and allows the hot gas stream,containing the drying gas, and evaporated water and solvents, to pass.Preferably, bag filter 262 is made from a material such as Gore-Tex®,available from W.L. Gore & Associate, Inc., Newark, Del. Dry particlesare collected at a product collection point 264 by running a back pulseof nitrogen across bag filter 262.

The collected particles can then be screened, for example, using sizescreening methods known to one skilled in the art. In one embodiment ofthe present invention, single dosages of the collected dry particles aremeasured, and the single dosages are then packaged, using techniqueswell known to one skilled in the art. In this manner, a unit dose of adry powder composition can be formed by placing a therapeuticallyeffective amount of dry powder composition made up of particles into aunit dose receptacle.

One embodiment of an atomizer suitable for use with the system depictedin FIG. 2 is a vaned rotary atomizer, such as rotary atomizer 300illustrated in FIG. 3. Rotary atomizer 300 includes a spinning wheel 320that spins about an axis 330. Liquid feed enters rotary atomizer 300 atan inlet point 302, and is distributed across wheel 320, as depictedgenerally at 304. Wheel 320 disperses the liquid feed into a spray offine droplets. The spin rate of the wheel is controlled, as is theliquid feed rate. By controlling the spin rate and liquid feed rate, thecharacteristics of the spray can be controlled, such as droplet size.Rotary atomizer 300 is configured with 24 vanes 310. It should bereadily apparent to one skilled in the art that rotary atomizers withother number of vanes 310 can be used with the present invention. Forexample, a rotary atomizer having 4 vanes, or a vaneless rotaryatomizer, could also be used.

Alternate embodiments of an atomizer suitable for use with the systemshown in FIG. 2 are shown in FIGS. 4A, 4B, 4C, 4D, 4E, and 5. FIGS. 4A,4B, 4C, 4D, and 5 depict two-fluid nozzles that atomize a liquid feedstream through the use of one or more gas streams that impinge upon theliquid feed stream. One example of an internal mixing nozzle 400, isillustrated in FIG. 4A. In the internal mixing nozzle 400, gas 420impinges on a liquid feed stream 410 in a mixing chamber 430 that isinternal to internal mixing nozzle 400. A spray of atomized droplets 440exits internal mixing nozzle 400 through a single hole. As would beapparent to one skilled in the art, any number of gas streams, includinga single gas stream, could be used.

FIG. 4B illustrates another example of an internal mixing nozzle, asingle-hole nozzle 450. The single-hole nozzle 450 operates under thesame principles as the internal mixing nozzle 400 depicted in FIG. 4A.The gas is supplied through inlet 451, and the liquid is suppliedthrough inlet 452. The gas impinges on the liquid in a mixing chamber458 in air cap 453. A spray of atomized droplets 457 exits thesingle-hole nozzle 450 through a single hole. The single-hole nozzlecomprises an air cap 453, a fluid cap 454, a retainer ring 455, and agasket 456.

FIG. 4C illustrates another example of an internal mixing nozzle, asix-hole nozzle 460. The six-hole nozzle operates under the sameprinciples as the single-hole nozzle, except that the air cap 461 in thesix-hole nozzle has six holes 462. The gas is supplied through inlet463, and the liquid is supplied through inlet 464. The gas impinges onthe liquid in a mixing chamber 468 in air cap 461. Sprays of atomizeddroplets 469 exit the six-hole nozzle 460 through holes 462. Thesix-hole nozzle comprises an air cap 461, a fluid cap 465, a retainerring 466, and a gasket 467.

FIG. 4D illustrates yet another example of an internal mixing nozzle, asheeting action nozzle 470. While this nozzle operates under principlessimilar to the single-hole and six-hole nozzles, the differentconfiguration of the nozzle depicted in FIG. 4D results in a differentatomizing effect. In nozzle 470, the liquid feed stream 471 enters themixing chamber 472 in a direction angular, and preferably lateral, tothe nozzle's longitudinal axis. Liquid feed stream 471 enters the mixingchamber 472 through a liquid feed inlet 476, which is at an angle to thelongitudinal axis of the nozzle 470. The liquid flows to and down thesides of the mixing chamber 472 in a thin sheet. The gas 473 impingesupon the thin sheet of liquid at the nozzle hole 474. A spray ofatomized droplets 475 exits the nozzle 470. One example of a nozzlesimilar in design to the nozzle depicted in FIG. 4D is the Flomax seriesof nozzles (Catalog #FM1) manufactured by Spraying Systems Co., Wheaton,Ill.

FIG. 4E illustrates yet another example of a nozzle, a pressure nozzle480, suitable for use with the system shown in FIG. 2. The pressurenozzle 480 does not need a gas stream to atomize droplets. Instead, ituses the pressure of the liquid to spray atomized droplets from thenozzle 480. Pressure applied to the liquid within the nozzle 480 forcesthe liquid out of the nozzle hole 481. A rotational force is imparted tothe liquid before it reaches the nozzle hole 481. This rotational forcemay be applied, for example, by a slotted insert 482 featuring multiplesmall cross-sectional feed inserts 483 leading to the nozzle hole 481.In the example depicted in FIG. 4E, the cross-sectional feed inserts 483are aligned on a diagonal to the nozzle hole 481. The spray of atomizeddroplets from each of the cross-sectional feed inserts 483 thereforeexits the nozzle hole 481 with angular momentum. Collectively, theangular momentum in the sprays from each of the cross-sectional feedinserts 483 yields a conical spray of atomized droplets.

FIG. 5 depicts an external mixing nozzle 500. In external mixing nozzle500, two gas streams 520 impinge on a liquid feed stream 510 in a mixingzone 530 that is adjacent to the external edge of external mixing nozzle500. A spray of atomized droplets 540 is formed external to externalmixing nozzle 500. As would be apparent to one skilled in the art, othernumbers of gas streams, including a single gas stream, could be used.

In order to produce particles optimized for inhalation and pulmonarydrug delivery, optimization experiments were conducted to enhanceporosity during the atomization step of the dry particle productionprocess. Through these experiments it was determined that changing themode of atomization affects porosity, and that porosity can becontrolled through the selection of the type of atomizer.

Three rotary atomizers were tested, all of which had a configurationsubstantially as shown in FIG. 3. The three atomizers differed in thenumber of vanes 310 on wheel 320. One had four vanes (“V4”), one had 24vanes (“V24”), and one was vaneless. The V4 and the V24 wheels wereoperated using similar process conditions, shown below in Table 1, toobtain particles with similar geometric sizes, shown below in Table 2.Because of the increased number of vanes, the V24 wheel could not beoperated at as a high an rpm as the V4 wheel. TABLE 1 Outlet Drying GasAtomizer Inlet Temperature Atomizer Pressure Feed Rate Wheel Temperature(° C.) (° C.) Speed (rpm) (mmH₂O) (mL/min) V4 120 55 50000 98 63 V24 12062 34000 110 60

TABLE 2 Geometric Size Measured @ Fine Particle Fraction (%) Run NumberWheel Type 0.5 bar 2 bar 3 bar 4 bar <5.6 μm <3.4 μm 294053 V4 9.5 8.9 86.7 72 56 294054 V24 9.2 7.5 6.5 5.3 65 48

The data in Table 2 suggest that particles produced using the V4 wheelare larger and more porous (e.g., have higher FPF(5.6) and FPF(3.4))than particles produced using the V24 wheel. One reason for thisdifference could be differences in “air pumping” between the twoatomizers. “Air pumping” occurs with rotary atomizers because, as thewheels spin, the wheels act as a fan, drawing air through the wheel. Atthe flow or feed rates to the atomizers typically used with the presentinvention, the V24 vanes do not completely fill with liquid.Consequently, there is a path for the air to flow over the liquid in thevane, with only a portion being entrained in the liquid to be atomized.The V4 vanes operate similarly, but because the vanes are physicallysmaller, the V4 vanes are usually filled with liquid during operation.Consequently, the air and atomization gas must both pass simultaneouslythrough the vane, rather than over the vane. This allows for a moreintimate contact between the air and liquid to be atomized. Thisintimate contact between gas and liquid induces more porosity in theresulting dry particle.

The increase of porosity in the particles resulting from the gas/liquidcontact can be seen by comparing the particles produced with vanedatomizers with particles produced using a vaneless atomizer. Vanelessatomizers do not generate a strong air pumping effect. A V4 and avaneless atomizer were operated using similar process conditions, shownbelow in Table 3. As can be seen from Table 4, the particles producedusing the vaneless atomizer were both smaller and more dense (lowerFPF(5.6) and FPF(3.4)) than the particles produced using the V4atomizer. TABLE 3 Outlet Drying Gas Atomizer Inlet Temperature AtomizerPressure Feed Rate Wheel Temperature (° C.) (° C.) Speed (rpm) (mmH₂O)(mL/min) V4 155 63 60000 98 52.5 Vaneless 155 63 50000 98 52.5

TABLE 4 Geometric Size Measured @ Fine Particle Fraction (%) Run NumberWheel Type 0.5 bar 2 bar 3 bar 4 bar <5.6 μm <3.4 μm 294088 V4 14.2 12.511.2 9.9 70 55 294089 Vaneless 5.4 5 4.8 4.2 63 40

In a preferred embodiment of the present invention, a two-fluid nozzleis used to increase the contact between gas and liquid during theatomization step to increase the porosity of the resulting dryparticles. As described above, a two-fluid nozzle is configured to allowfor mixing of two fluids, such as a gas and a liquid, duringatomization. The mixing can occur either externally (using, for example,a nozzle such as that shown in FIG. 5) or internally (using, forexample, a nozzle such as that shown in FIG. 4A, 4B, 4C, or 4D) withrespect to the nozzle itself. Examples using the mixing nozzles shown inFIG. 4A, 4B, 4C, 4D, or 4E are disclosed below in connection with Tables14-25.

Experiments were conducted with an external mixing nozzle substantiallyas shown in FIG. 5 at nozzle or system pressures ranging from 15 to 40psi. As shown below in Table 5, the FPF(5.6) ranged from 76 to 81% andthe FPF(3.4) ranged from 59 to 63%. Changes in porosity as a function ofincreasing gas rates were not observed with external mixing nozzles.TABLE 5 System Nozzle Geometric Size Measured @ Fine Particle Fraction(%) Run Number Pressure (psi) 0.5 bar 2 bar 3 bar 4 bar <5.6 μm <3.4 μm294141 15 9.4 8.4 7.3 5.3 81 63 294132C 20 9.5 7.5 6.7 4.9 77 61 294132B40 8.4 9.4 7.1 6.4 76 59

Experiments were conducted using an internal mixing nozzle substantiallyas shown in FIG. 4A. Use of internal mixing nozzles likely allows formore intimate contact between the liquid and gas, thereby resulting indry particles having higher porosity, as evidenced by higher FPF(5.6)and FPF(3.4). Experiments were conducted to test the effect of nozzlepressure and the effect of the mass flow ratio of gas to liquid. Asevidenced by the data in Table 6 below, more porous particles can beobtained at higher operating pressures with an internal mixing nozzle.The pressure effect may be a reflection of the higher gas/liquid ratioof run 294152A (1.8) compared to that of run 294151 (1.3). As evidencedby the data in Table 7 below, more porous particles can be obtained athigher gas:liquid flow rates with an internal mixing nozzle. Theoperating conditions for use with an internal mixing nozzle thatoptimized the geometric size and the porosity/fine particle fraction areshown below in Table 8. TABLE 6 System Nozzle Geometric Size Measured @Fine Particle Fraction (%) Run Number Pressure (psi) 0.5 bar 2 bar 3 bar4 bar <5.6 μm <3.4 μm 294151 68 12 10.3 8.8 7.2 76 64 294152A 100 11.58.8 8.3 7.4 86 79

TABLE 7 Gas/Liquid Geometric Size Measured @ Fine Particle Fraction (%)Run Number Ratio 0.5 bar 2 bar 3 bar 4 bar <5.6 μm <3.4 μm 294150A 112.9 12.3 10.1 8.1 76 64 294150C 1.5 14 11.8 9.8 7.8 82 70

TABLE 8 Run Gas/Liquid System Nozzle Geometric Size Measured @ FineParticle Fraction (%) Number Ratio Pressure (psi) 0.5 bar 2 bar 3 bar 4bar <5.6 μm <3.4 μm 342012B 1.9 58 10.8 10.4 8 6.5 90 81

As noted above, the present invention advantageously optimizes processconditions for increasing and controlling the porosity of the dryparticles through the use of the internal mixing two-fluid nozzle. Inanother aspect of the present invention, particle porosity is increasedthrough the use of volatile salts. Carbonation of one of the liquidcomponents used to form the dry particles induces porosity in theresulting dried particles by nucleation of carbon dioxide (CO₂). Thenucleation of CO₂ induces multiple phases (gas and liquid) in anatomized droplet, with the gas phase being inaccessible for theexcipients. Such heterogeneous nature of the atomized droplet leads toincreased porosity in the resulting dry particle once drying iscomplete. The tap density of the dry particles can be used as a measureof porosity. The more porous the dry particles, the lower the observedtap density. It has been found that particles spray dried from acarbonated formulation solution have much lower tap density thanparticles spray dried from an otherwise identical solution.

An experiment was conducted using a formulation of 60/18/18/4(DPPC/Lactose/Albumin/Albuterol sulfate). Four batches were prepared.The aqueous phase of two batches were sparged with CO₂, the other twowere not treated with CO₂. The spray dry conditions were well controlledfor all four batches so that they were operated at the same processcondition. A vaned rotary atomizer (V24) was used in this experiment.The results are shown in Table 9 below. TABLE 9 Outlet T Feed RateAtomizer Tap Density Batch No. Sparging CO₂ Inlet T (° C.) (° C.)(ml/min) Speed (rpm) (g/cc) 1 No 110 56-57 40 18000 0.09 2 Yes 110 56-5740 18000 0.065 3 No 110 56-57 40 18000 0.091 4 Yes 110 56-57 40 180000.059

From the data shown in Table 9 above, it is quite clear that particlesmanufactured by the solution sparged with CO₂ have lower tap density,with a more porous structure. Therefore, sparging the spray dryingsolution with CO₂ helps to increase porosity of the particles.

In a preferred aspect of the present invention, increased porosity, andconsequently lower tap density, can be achieved through the use ofammonium bicarbonate (NH₄HCO₃) in one of the liquid components used toform the dry particles. In an alternate embodiment of the presentinvention, carbonation of one of the liquid components, or of thecombination solution, could be achieved by sparging with CO₂ at reducedtemperature (4° C.) or pressurizing with CO₂, also preferably at reducedtemperature. The carbonate components (HCO₃ ⁻/CO₃ ²⁻/CO₂) would notremain in the final dry particles as they are volatile species. Theywould be eliminated during the drying process. Use of carbonatecomponents or other volatile salts have the advantage of avoiding theuse of higher temperatures for inducing porosity. Additionally,carbonate components can advantageously be used over mild pH rangeswhere protein stability is maximized. Moreover, the pH of the resultingdry particles can be adjusted through the addition of appropriatecounter ions.

As described above, the addition of volatile salts to the solution usedto form dry particles increases the porosity of the particles. Theaddition of volatile salts also increases the production of insolublecomplexes, the production of which can be used to control the releaserate of the active agent in the particles, both proteins and smallmolecules. The formation of an insoluble complex begins with theinteraction between, for example, two species when they are dissolvedtogether. In solution, molecules of opposite charge are attracted toeach other via electrostatic forces. When the ionic species are limitedto oppositely charged forms A and B, then A and B will attract to eachother. If A and B interact strongly enough, they are likely to form aninsoluble complex A_(x)B_(y), where x and y are the stoichiometriccoefficients describing the ratio(s) with which A and B tend toassociate. This complex can stay in suspension, or may form aprecipitate that will settle or flocculate. If additional ionic speciesare present, the additional species will compete with A and B on acharge basis and tend to reduce the strength of the interaction betweenA and B, thereby decreasing the tendency of A and B to form an insolublecomplex. If the additional ionic species can be selectively removed, Aand B will then form an insoluble complex.

Insoluble material can interfere with the production of large porousparticles that are of particular utility for pulmonary drug delivery. Itis often desirable to have large porous particles that contain species Aand B, where A and B have the tendency to form an insoluble complexA×B_(y). Higher ionic strength decreases the strength of the interactionbetween A and B, rendering A and B more soluble in the process solution.As the material is spray dried, the volatile salt is preferentiallyremoved from the droplets as the dry particles are formed. The insolublecomplex A_(x)B_(y) may subsequently form in the nearly-dried particles,but the porous structure has already formed in those particles.

The following non-limiting examples illustrate the use of ammoniumbicarbonate to produce particles having a low aerodynamic diameter,which results in a low tap density and high porosity. It should beunderstood by one skilled in the art that the present invention is notlimited to the use of ammonium bicarbonate, and that other suitablevolatile salts could also be used without departing from the scope ofthe invention.

EXAMPLES Porous Bovine Albumin Particles

350 mg of bovine serum albumin, 100 mg of anhydrous sodium citrate, 66mg of calcium chloride dihydrate, and 10 g of ammonium bicarbonate weredissolved in 500 mL of sterile water. The resulting feed solution wasspray dried using a Niro spray dryer equipped with a rotary atomizer.The drying gas (dry nitrogen) was delivered at a flow rate ofapproximately 100 kg/h with a 170° C. inlet temperature, and a 61° C.outlet temperature. The feed solution was delivered to theatomizer/spray dryer at 60 ml/min liquid flow rate. The atomizer wasoperated at 29,000 rpm, with −2 inches of water pressure in the sprayingchamber of the spray dryer. The resulting dry particles had a mass meanaerodynamic diameter of 4.03 μm, and a volume mean geometric diameter of7.76 μm at 1 bar.

48 mg of bovine serum albumin, 20 mg of anhydrous sodium citrate, 13 mgof calcium chloride dihydrate, 28 mg of maltodextrin (M100) and 10 g ofammonium bicarbonate were dissolved in 1000 mL of sterile water. Theresulting feed solution was spray dried using a Niro spray dryerequipped with a rotary atomizer. The drying gas (dry nitrogen) wasdelivered at a flow rate of approximately 100 kg/h with a 170° C. inlettemperature, and a 56° C. outlet temperature. The feed solution wasdelivered to the atomizer/spray dryer at 60 ml/min liquid flow rate. Theatomizer was operated at 29,000 rpm, with −2 inches of water pressure inthe spraying chamber of the spray dryer. The resulting dry particles hada mass mean aerodynamic diameter of 3.97 μm, and a volume mean geometricdiameter of 15.01 μm at 1 bar.

Porous Humanized IgG Antibody Particles

47.35 ml of 50.7 mg/ml humanized monoclonal IgG1 antibody solution wasadded to 1000 mL water (pH=6.4). 1.6 g of DPPC was added to 1000 mLisopropyl alcohol. The two solutions were mixed by slowly adding theethanol solution to the aqueous solution immediately prior to spraydrying. The resulting feed solution was spray dried using a Niro spraydryer equipped with a rotary atomizer. The drying gas (dry nitrogen) wasdelivered at a flow rate of approximately 110 kg/h with a 100° C. inlettemperature, and a 45° C. outlet temperature. The feed solution wasdelivered to the atomizer/spray dryer at 50 ml/min liquid flow rate. Theatomizer was operated at 34,500 rpm, with −2 inches of water pressure inthe spraying chamber of the spray dryer. The resulting dry particles hada mass mean aerodynamic diameter of 3.01 μm, and a volume mean geometricdiameter of 9.17 μm at 1 bar.

Porous Human Growth Hormone Particles

2.63 g hGH, 1.03 g sucrose, 1.58 g leucine, 368 mg sodium phosphate,26.25 mg Tween-20, and 52.5 g ammonium bicarbonate was added to 3675 mLwater (pH=7.4). 1575 mL of ethanol was slowly added to the aqueoussolution immediately prior to spray drying. The resulting feed solutionwas spray dried using a Niro spray dryer equipped with a rotaryatomizer. The drying gas (dry nitrogen) was delivered at a flow rate ofapproximately 110 kg/h with a 139° C. inlet temperature, and a 62° C.outlet temperature. The feed solution was delivered to theatomizer/spray dryer at 60 ml/min liquid flow rate. The atomizer wasoperated at 34,000 rpm, with −5 inches of water pressure in the sprayingchamber of the spray dryer. The resulting dry particles had a mass meanaerodynamic diameter of 1.94 μm, and a volume mean geometric diameter of5.8 pm at 1 bar.

Particles containing 93 wt % hGH and 7 wt % sodium phosphate wereprepared as follows. The aqueous solution was prepared by adding 328 mgof sodium phosphate monobasic to 400 mL of water for irrigation (Braun).The pH was adjusted to 7.4 using 1.0 N NaOH. 15 g of ammoniumbicarbonate (Spectrum Chemicals) was added to the sodium phosphatebuffer. 200 mL of ethanol (Pharmco) was added to complete the aqueoussolution. The aqueous solution was combined in a static mixer with 400mL of 14 g/L hGH solution (5.6 g hGH dissolved in sodium phosphatebuffer at pH=7.4). The combined solution was spray dried under thefollowing process conditions:

Inlet temperature ˜115° C.

Outlet temperature from the drying drum ˜70° C.

Nitrogen drying gas=110 kg/hr

Nitrogen atomization gas=46 g/min

2 Fluid internal mixing nozzle atomizer

Nitrogen atomization pressure ˜65 psi

Liquid feed rate=25 ml/min

Liquid feed temperature ˜22° C.

Pressure in drying chamber=−2.0 in water

The resulting particles had a FPF(5.6) of 84%, and a FPF(3.4) of 77%,both measured using a 2-stage ACI. The volume mean geometric diameterwas 8.9 μm at 1.0 bar.

Porous Albuterol Sulfate Particles

80 mg of albuterol sulfate, 460 mg of maltodextrin, 350 mg of leucine,110 mg of Pluronic F68, and 10 g of ammonium bicarbonate were dissolvedin 500 mL of sterile water. The aqueous solution was mixed with 500 mLof ethanol. The resulting feed solution was spray dried using a Nirospray dryer equipped with a rotary atomizer. The drying gas (drynitrogen) was delivered at a flow rate of approximately 100 kg/h with a150° C. inlet temperature, and a 62° C. outlet temperature. The feedsolution was delivered to the atomizer/spray dryer at 65 ml/min liquidflow rate. The atomizer was operated at 22,000 rpm, with 39 mm of waterpressure in the spraying chamber of the spray dryer. The resulting dryparticles had a mass mean aerodynamic diameter of 3.33 μm, and a volumemean geometric diameter of 11.5 μm at 4 bar.

Porous Danazol Particles

800 mg of danazol, 1.6 g of maltodextrin, 1.2 g leucine, 400 mg ofpolyethyleneglycol (PEG) 1500, and 40 g of ammonium bicarbonate weredissolved in 2 L of sterile water. The aqueous solution was mixed with 2L of ethanol. The resulting feed solution was spray dried using a Nirospray dryer equipped with a rotary atomizer. The drying gas (drynitrogen) was delivered at a flow rate of approximately 100 kg/h with a155° C. inlet temperature, and a 64° C. outlet temperature. The feedsolution was delivered to the atomizer/spray dryer at 70 ml/min liquidflow rate. The atomizer was operated at 22,000 rpm, with 39 mm of waterpressure in the spraying chamber of the spray dryer. The resulting dryparticles had a mass mean aerodynamic diameter of 2.69 μm, and a volumemean geometric diameter of 10.6 μm at 4 bar.

Turning now to FIG. 6, an alternate embodiment of a system 600 forproducing dry particles is shown. System 600 will be explained for theexemplary situation of combining an aqueous solution 610 with an ethanolsolution 620 to form dry particles. As would be readily apparent to oneskilled in the art, system 600 is not limited to use of an aqueoussolution and an ethanol solution. For example, system 600 could be usedto combine other hydrophilic and hydrophobic components, other aqueousand organic components, or a hydrophilic component and an organicsolvent, to form dry particles. System 600 could also be used to combinetwo components to form dry particles where the combination of the twocomponents causes degradation in one of the components.

As illustrated in FIG. 6, aqueous solution 600 is transported via a gearpump 614 and a flow meter 612 to a static mixer 630. Ethanol (EtOH)solution 620 is transported via a gear pump 624 and a flow meter 622 tostatic mixer 630. In one embodiment of the present invention, the samevolume of aqueous solution 610 and ethanol solution 620 is used, andpumps 614 and 624 are operated at substantially the same rate to deliverthe respective solutions to static mixer 630 at substantially the samerate. In other embodiments, pumps 614 and 624 are operated at differentrates. As would be apparent to one skilled in the art, the concentrationof components in the final dry particles can be used to determine thepump rates for pumps 614 and 624. For example, in one embodiment of thepresent invention, the volumes of aqueous solution 610 and ethanolsolution 620 are selected to each be completely consumed during thespray drying process. In such an embodiment, the pump rates for pumps614 and 624 are selected so that solutions 610 and 620 are both used up.As would be appreciated by one skilled in the art, other types of pumps,or other means for transporting the solutions to static mixer 630 couldbe used. Alternatively, a single pump could be used to deliver bothsolutions to static mixer 630. In the embodiment shown in FIG. 6, staticmixer 630 is oriented in a vertical configuration, i.e., a central axisof static mixer 630 is parallel to a central axis of a spray dryer 650.Alternatively, static mixer 630 could be configured in an inclinedconfiguration, at an acute angle with respect to the central axis ofspray dryer 650. The inclined or vertical configuration of static mixer630 helps ensure laminar flow, with any bubbling or gassing at the top.Preferably, the inputs to the static mixer flow upwards to provide morehomogeneous mixing, and to prevent channeling. Static mixers suitablefor use with the present invention are illustrated in FIGS. 1A and 1B,and include model 1/4-21, made by Koflo Corporation.

An outlet end of static mixer 630 is in fluid communication with atwo-fluid nozzle 640 that is used to atomize the combination flowing outof static mixer 630 into droplets. In an alternative embodiment ofsystem 600, a rotary atomizer, such as rotary atomizer 300 depicted inFIG. 3, is used in place of nozzle 640. Because the combination flowingout of static mixer 630 is a homogeneous mixture of the input liquidcomponents (aqueous solution and ethanol solution), the droplets formedby nozzle 640 will also contain a homogeneous mixture of the inputliquid components. Nozzle 640 can be an internal mixing nozzle such asthat shown in FIG. 4, or an external mixing nozzle such as that shown inFIG. 5. Preferably, nozzle 640 is an internal mixing nozzle.

In the embodiment shown in FIG. 6, a nitrogen gas stream 642 is input tonozzle 640 to atomize the combination flowing out of static mixer 630.As discussed above with respect to FIGS. 4 and 5, nitrogen gas stream642 can be a single gas stream, or divided into a plurality of gasstreams, to impinge upon the liquid combination to atomize it intodroplets. As would be readily apparent to one skilled in the art, othergases could be used to atomize the liquid combination into droplets, andthe present invention is not limited to the use of nitrogen as theatomizing gas stream.

The atomized droplets from nozzle 640 are dried in spray dryer 650.Nitrogen from a nitrogen gas supply 652 is heated by a heater 654 andinput to spray dryer 650. A flow meter 656 and a temperature measurementpoint 658 are used to monitor the flow and temperature of the nitrogengas input to spray dryer 650. As would be readily apparent to oneskilled in the art, other drying gases could be used in spray dryer 650,such as, but not limited to, air, argon, carbon dioxide, helium, andcombinations or mixtures thereof. In an alternate embodiment of thepresent invention, the drying gas input to spray dryer 650 is the sameinput used to atomize the liquid combination in nozzle 640. A mixture ofgas and dried particles or powder exits from spray dryer 650 at anoutlet 659. A flow conditioner 660 and temperature measurement point 662are used to condition and monitor the characteristics of the gas-powdermixture exiting spray dryer 650. A flow conditioner suitable for usewith the present invention is made by Vortab, San Marcos, Calif.

Flow conditioner 660 conditions the gas-powder mixture exiting spraydryer 650 so that the particles contained in the gas stream can becharacterized by measuring the geometric diameter and the aerodynamicdiameter of the particles. Flow conditioner 660 provides a morehomogeneous powder distribution in the piping by imparting turbulentconditions to the gaseous stream. The more homogeneous powderdistribution prevents selective or skewed sampling in the downstreamsizers. After conditioning by flow conditioner 660, a sample of thegas-powder mixture flows through a geometric sizer 670 and anaerodynamic sizer 672, the operation of which will be discussed in moredetail below. The sample of the gas-powder mixture is used to determinegeometric and aerodynamic size. After sizing, the sample is deposited ona filter (not shown) for later disposal. The bulk of the gas-powdermixture flows directly out of flow conditioner 660 and the dry particlesare collected on a bag filter 680 that retains the dry particle productwhile allowing the gas to pass through to an exhaust 684 and for solventstripping. The dry particle product is removed from bag filter 680, suchas by running a back pulse of nitrogen across bag filter 680, and iscollected in a product collection vessel 682.

Geometric sizer 670 preferably measures volume median geometric diameter(VMGD) of the particles. An exemplary geometric sizer is the Insiteconline particle sizer, available from Malvern Instruments Ltd. TheInsitec device consists of an optical sensor head, a signal processingunit, and a computer for instrument control and data collection andanalysis. Aerodynamic sizer 672 preferably measures mass medianaerodynamic diameter (MMAD) of the particles. An exemplary aerodynamicsizer is the PS Model 3321, available from TSI, Inc., St. Paul, Minn. Inone embodiment of the present invention, a computer 674 is coupled togeometric sizer 670 and to aerodynamic sizer 672. Computer 674 is usedto carry out the optimization process of the present invention,described in more detail below with respect to FIG. 7. In an alternateembodiment of the present invention, a computer or processor that ispart of aerodynamic sizer 672 or geometric sizer 670 is used to carryout the optimization process of the present invention.

Conventional optimization of a spray drying process is a time consumingand material intensive process, requiring the manipulation of multipleprocess variables, such as inlet temperature, outlet temperature,atomizer speed, drum pressure, gas flow rate, and liquid feed rate, andmultiple product formulations. A typical optimization run would involveselecting a formulation and a set of process conditions, spraying thematerial under the selected conditions, collecting the finished dryparticle powder, and characterizing the dry particles using various invitro techniques, such as laser diffraction techniques (HELOSdiffractometer and a RODOS disperser) to measure geometric diameter, anaerosizer to measure aerodynamic diameter, an ACI to measure sizedistribution, and measurement of tap density. Once the results of thecharacterization tests were complete, then the process parameters couldbe adjusted to optimize the characteristics of the particles.Approximately 2-3 g of material, and about two hours, are required foreach such optimization run. To completely optimize process conditions toobtain final desired powder characteristics, hundreds of runs may berequired. Thus, conventional optimization of the spray drying process isinefficient, time consuming, and expensive.

The system and method of the present invention significantly decreasesthe time and material required to optimize the spray drying process.Using the system and method of the present invention, an operator canevaluate particle characteristics in real time during the spray dryingprocess without having to run the traditional in vitro characterizationassays after the fact. Using the system and method of the presentinvention, process conditions can be modified in real time to optimizeparticle size to produce particles having a desired geometric and/oraerodynamic diameter.

Geometric sizer 670 can be used to measure the geometric diameter of theparticles, and aerodynamic sizer 672 can be used to measure theaerodynamic diameter of the particles. However, in order for theaerodynamic measurement to be made, the density of the particles must beknown prior to the measurement. Density (ρ), geometric diameter (d_(g)),and aerodynamic diameter (d_(a)) are related by the following equation:d_(a)=d_(g) √{square root over (ρ)}. The process of the presentinvention uses density as the optimization variable to achieve particleshaving the desired aerodynamic and/or geometric diameters.

One embodiment of a process of the present invention for optimizingparticle size is illustrated in FIG. 7. In a step 710, an initialparticle density is selected, and provided to aerodynamic sizer 672. Ina preferred embodiment of the present invention for preparation of dryparticles suitable for inhalation into the lung, preferably into thedeep lung, an initial particle density of 0.06 g/cm³ is used. It shouldbe apparent to one skilled in the art that other initial particledensities can be selected, depending upon the particular particle to beproduced. In a step 720, a measured aerodynamic diameter (d_(a) ^(m))and a measured geometric diameter (d_(g) ^(m)) are obtained usingaerodynamic sizer 672 and geometric sizer 670, respectively. In a step730, a calculated geometric diameter (d_(g) ^(c)) is calculated from theinitial particle density and the measured aerodynamic diameter using theequationd_(a) ^(m)=d_(g) ^(c)√{square root over (ρ)}

If the estimated initial particle density (e.g., 0.06 g/cm³) was correctfor the particles being produced, then the calculated geometric diametershould be substantially equal to the measured geometric diametermeasured by geometric sizer 670. If the calculated geometric diameterand the measured geometric diameter do not match, then a new density isinput into aerodynamic sizer 672 and processing returns to step 730 tore-calculate geometric diameter. This process continues until thecalculated geometric diameter and the measured geometric diameter match.This iterative process is illustrated in FIG. 7. In a step 740, it isdetermined whether d_(g) ^(c)=d_(g) ^(m). The calculated geometricdiameter is compared to the measured geometric diameter to determine adifferential. If there is a differential, then, in a step 760, theparticle density is adjusted, and processing returns to step 730 toagain calculate geometric diameter using the adjusted value for particledensity. Increasing the density decreases the geometric diameter.Decreasing the density increases the geometric diameter. The geometricdiameter is again calculated in step 730, and compared to the measuredgeometric diameter in step 740. This process repeats until in step 740it is determined that the calculated geometric diameter is substantiallyequal to the measured geometric diameter, at which point the particleproduction process continues, as shown in a step 750.

When using the process of the present invention as shown in FIG. 7,solutions are spray dried to form dry particles, and the aerodynamic andgeometric diameters are measured. Process conditions (flow rates,temperatures, etc.) are held constant during the measurement of theaerodynamic and geometric diameters. Once the measurements are made,solvents can then be run through the spray drying system while thedensity iteration is calculated (steps 730, 740, and 760 in FIG. 7).This represents a significant savings of costly material, such as theaqueous solution containing active agent.

In one embodiment of the present invention, the density iteration isdone with aerodynamic diameter as a fixed variable. In such anembodiment, the density is changed until the calculated geometricdiameter is substantially equal to the measured geometric diameter. Oncethe density iteration is complete, then the density, aerodynamicdiameter, and geometric diameter of the particles are known. At thatpoint, process conditions (gas and/or liquid flow rates, temperatures,process solutions) can be changed to achieve a different density,aerodynamic, or geometric diameter. Alternatively, a process conditionor process solution can be modified to determine its affect on density,aerodynamic diameter and geometric diameter.

In another embodiment of the present invention, the density iteration isdone with geometric diameter as a fixed variable. In such an embodiment,process conditions, such as gas flow rate, are adjusted to achieve adesired measured geometric diameter. Aerodynamic diameter is measured.Density is then changed until the calculated geometric diameter issubstantially equal to the measured geometric diameter. Once the densityiteration is complete, then the density, aerodynamic diameter, andgeometric diameter of the particles are known. By fixing geometricdiameter in the density optimization process, particles having the samegeometric diameter can be produced under different process conditions tofacilitate comparisons between particles of the same geometric diameter.

Once the process reaches step 750, an operator has three values to usein decisions regarding the dry particles that have been produced to thatpoint: geometric diameter; aerodynamic diameter; and density. Oneadvantage of the method of the present invention is that the liquidcombination from static mixer 630 needs to be atomized into spray dryer650 for only about three minutes for the data to be collected and step750 reached for a particular set of process conditions. In this manner,multiple sets of process conditions can be rapidly screened using aminimal amount of material. For example, once step 750 is reached, thedensity, geometric diameter, and aerodynamic diameter of the particlesare known for a given set of process conditions and process solutions.If the desired density, geometric diameter, or aerodynamic diameter hasnot been achieved, then the process conditions can be modified and thedensity iteration process repeated. Alternatively, a particular processcondition or process material can be changed, and its affect on density,aerodynamic diameter, and geometric diameter determined.

To produce dry particles that can penetrate deep into the lung, thedesired geometric diameter is in the range of from about 7 to about 10μm. Using the method and apparatus of the present invention as depictedin FIGS. 6 and 7, the density used by aerodynamic sizer 672 is adjustedto minimize particle density, while the measured geometric diameter isheld constant in the 7-10 μm range. For example, dry particlescontaining hGH were made using the apparatus substantially as shown inFIG. 6 by selecting an initial particle density of 0.06 g/cm³. Thedesired geometric diameter size range for reaching the deep lung is inthe range of from about 7 to about 10 μm, and aerodynamic diameter sizerange of from about 1 to about 3 μm. The aerodynamic diameter wasmeasured using the initial particle density of 0.06 g/cm³, and thegeometric diameter was measured. The geometric diameter was calculated,and compared to the measured geometric diameter. To reach the deep lung,the measured geometric diameter, and consequently the calculatedgeometric diameter, should be in the range of from about 7 to about 10μm. If the calculated geometric diameter was not the same as themeasured geometric diameter, the density value used in the aerodynamicsizer was reduced, and the process repeated. By minimizing particledensity and holding the geometric diameter constant in the desiredrange, particles having the desired geometric diameter, as well as thedesired low aerodynamic diameter, were produced.

The use of density as a valid optimization variable for producingparticles of the desired aerodynamic diameter is demonstrated by thegraph shown in FIG. 9. FIG. 9 shows a graph of mass median aerodynamicdiameter (MMAD) in μm as measured using the system and method of thepresent invention described above with reference to FIGS. 6 and 7,versus MMAD measured using a conventional multi-stage liquid impinger(MSLI). A MSLI works on the same basic principles as an ACI devicedescribed above. However, instead of having dry metal plates for stageslike an ACI, a MSLI has liquid-containing stages. Each MSLI stageconsists of an ethanol-wetted glass frit. The wetted stage is used toprevent bouncing and re-etrainment, which can occur using the ACI. Thepurpose of the liquid is to eliminate the presence of bounce in thesystem, typically leading to greater accuracy than an ACI. The MSLI usedfor the data illustrated in FIG. 9 included 5 stages. As can be seenfrom FIG. 9, the MMAD measured using the density iteration process ofthe present invention (y-axis) correlated well with the MMAD measuredusing an MSLI (x-axis), with the MMAD measured using the densityiteration process being a reliable predictor of trends in MMAD measuredusing the MSLI.

As noted above with respect to FIGS. 6 and 7, a computer or computersystem can be used to control the aerodynamic and/or geometric particlesizers, and to carry out the particle size optimization process. Anexemplary computer system suitable for use with the present invention isshown in FIG. 8. The computer system 802 includes one or moreprocessors, such as a processor 804. The processor 804 is connected to acommunication bus 806. After reading this description, it will becomeapparent to a person skilled in the relevant art how to implement theinvention using other computer systems and/or computer architectures.

The computer system 802 also includes a main memory 808, preferablyrandom access memory (RAM), and can also include a secondary memory 810.The secondary memory 810 can include, for example, a hard disk drive 812and/or a removable storage drive 814, representing a floppy disk drive,a magnetic tape drive, an optical disk drive, etc. The removable storagedrive 814 reads from and/or writes to a removable storage unit 818 in awell-known manner. The removable storage unit 818, represents a floppydisk, magnetic tape, optical disk, etc. which is read by and written toby the removable storage drive 814. As will be appreciated, theremovable storage unit 818 includes a computer usable storage mediumhaving stored therein computer software and/or data.

In alternative embodiments, the secondary memory 810 may include othersimilar means for allowing computer programs or other instructions to beloaded into the computer system 802. Such means can include, forexample, a removable storage unit 822 and an interface 820. Examples ofsuch can include a program cartridge and cartridge interface (such asthat found in video game devices), a removable memory chip (such as anEPROM, or PROM) and associated socket, and other removable storage units822 and interfaces 820 which allow software and data to be transferredfrom the removable storage unit 822 to the computer system 802.

The computer system 802 can also include a communications interface 824.The communications interface 824 allows software and data to betransferred between the computer system 802 and external devices.Examples of the communications interface 824 can include a modem, anetwork interface (such as an Ethernet card), a communications port, aPCMCIA slot and card, etc. Software and data transferred via thecommunications interface 824 are in the form of signals 826 that can beelectronic, electromagnetic, optical or other signals capable of beingreceived by the communications interface 824. Signals 826 are providedto communications interface via a channel 828. A channel 828 carriessignals 826 and can be implemented using wire or cable, fiber optics, aphone line, a cellular phone link, an RF link and other communicationschannels.

In this document, the terms “computer program medium” and “computerusable medium” are used to generally refer to media such as theremovable storage device 818, a hard disk installed in hard disk drive812, and signals 826. These computer program products are means forproviding software to the computer system 802.

Computer programs (also called computer control logic) are stored in themain memory 808 and/or the secondary memory 810. Computer programs canalso be received via the communications interface 824. Such computerprograms, when executed, enable the computer system 802 to perform thefeatures of the present invention as discussed herein. In particular,the computer programs, when executed, enable the processor 804 toperform the features of the present invention. Accordingly, suchcomputer programs represent controllers of the computer system 802.

In an embodiment where the invention is implemented using software, thesoftware may be stored in a computer program product and loaded into thecomputer system 802 using the removable storage drive 814, the harddrive 812 or the communications interface 824. The control logic(software), when executed by the processor 804, causes the processor 804to perform the functions of the invention as described herein.

In another embodiment, the invention is implemented primarily inhardware using, for example, hardware components such as applicationspecific integrated circuits (ASICs). Implementation of such a hardwarestate machine so as to perform the functions described herein will beapparent to persons skilled in the relevant art(s). In yet anotherembodiment, the invention is implemented using a combination of bothhardware and software.

In a preferred embodiment, the spray dried particles of the inventionhave a tap density less than about 0.4 g/cm³. Particles that have a tapdensity of less than about 0.4 g/cm³ are referred to herein as“aerodynamically light particles”. More preferred are particles having atap density less than about 0.1 g/cm³. Tap density can be measured byusing instruments known to those skilled in the art such as, but notlimited to, the Dual Platform Microprocessor Controlled Tap DensityTester (Vankel Technology, Cary, N.C.) or a GeoPyc™ instrument(Micrometrics Instrument Corp., Norcross, Ga. 30093). Tap density is astandard measure of the envelope mass density. Tap density can bedetermined using the method of USP Bulk Density and Tapped Density,United States Pharmacopoeia convention, Rockville, Md., 10^(th)Supplement, 4950-4951, 1999. Features that can contribute to low tapdensity include irregular surface texture and porous structure.

The envelope mass density of an isotropic particle is defined as themass of the particle divided by the minimum sphere envelope volumewithin which it can be enclosed. In one embodiment of the invention, theparticles have an envelope mass density of less than about 0.4 g/cm³.

Aerodynamically light particles have a preferred size, e.g., a volumemedian geometric diameter (VMGD) of at least about 5 μm. In oneembodiment, the VMGD is from about 5 μm to about 30 μm. In anotherembodiment of the invention, the particles have a VMGD ranging fromabout 10 μm to about 30 μm. In other embodiments, the particles have amedian diameter, mass median diameter (MMD), a mass median envelopediameter (MMED) or a mass median geometric diameter (MMGD) of at least 5μm, for example from about 5 μm to about 30 μm.

The diameter of the spray-dried particles, for example, the VMGD, can bemeasured using a laser diffraction instrument (for example Helos,manufactured by Sympatec, Princeton, N.J.). Other instruments formeasuring particle diameter are well known in the art. The diameter ofparticles in a sample will range depending upon factors such as particlecomposition and methods of synthesis. The distribution of size ofparticles in a sample can be selected to permit optimal deposition totargeted sites within the respiratory tract.

Aerodynamically light particles preferably have “mass median aerodynamicdiameter” (MMAD), also referred to herein as “aerodynamic diameter”,between about 1 μm and about 5 μm. In another embodiment of theinvention, the MMAD is between about 1 μm and about 3 μm. In a furtherembodiment, the MMAD is between about 3 μm and about 5 μm.

Experimentally, aerodynamic diameter can be determined by employing agravitational settling method, whereby the time for an ensemble ofparticles to settle a certain distance is used to infer directly theaerodynamic diameter of the particles. An indirect method for measuringthe mass median aerodynamic diameter (MMAD) is the multi-stage liquidimpinger (MSLI).

Particles that have a tap density, less than about 0.4 g/cm³, mediandiameters of at least about 5 μm, and an aerodynamic diameter of betweenabout 1 μm and about 5 μm, preferably between about 1 μm and about 3 μm,are more capable of escaping inertial and gravitational deposition inthe oropharyngeal region, and are targeted to the airways, particularlythe deep lung. The use of larger, more porous particles is advantageoussince they are able to aerosolize more efficiently than smaller, denseraerosol particles such as those currently used for inhalation therapies.

In another embodiment of the invention, the particles have an envelopemass density, also referred to herein as “mass density” of less thanabout 0.4 g/cm³. Particles also having a mean diameter of between about5 μm and about 30 μm are preferred. Mass density and the relationshipbetween mass density, mean diameter and aerodynamic diameter arediscussed in U.S. application Ser. No. 08/655,570, filed on May 24,1996, which is incorporated herein by reference in its entirety. In apreferred embodiment, the aerodynamic diameter of particles having amass density less than about 0.4 g/cm³ and a mean diameter of betweenabout 5 μm and about 30 μm mass mean aerodynamic diameter is betweenabout 1 μm and about 5 μm.

In comparison to smaller, relatively denser particles the largeraerodynamically light particles, preferably having a median diameter ofat least about 5 μm, also can potentially more successfully avoidphagocytic engulfment by alveolar macrophages and clearance from thelungs, due to size exclusion of the particles from the phagocytes'cytosolic space. Phagocytosis of particles by alveolar macrophagesdiminishes precipitously as particle diameter increases beyond about 3μm. Kawaguchi, H., et al., Biomaterials 7: 61-66 (1986); Krenis, L. J.and Strauss, B., Proc. Soc. Exp. Med., 107: 748-750 (1961); and Rudt, S,and Muller, R. H., J. Contr. Rel., 22: 263-272 (1992). For particles ofstatistically isotropic shape, such as spheres with rough surfaces, theparticle envelope volume is approximately equivalent to the volume ofcytosolic space required within a macrophage for complete particlephagocytosis.

The particles may be fabricated with the appropriate material, surfaceroughness, diameter and tap density for localized delivery to selectedregions of the respiratory tract such as the deep lung or upper orcentral airways. For example, higher density or larger particles may beused for upper airway delivery, or a mixture of varying sized particlesin a sample, provided with the same or different therapeutic agent maybe administered to target different regions of the lung in oneadministration. Particles having an aerodynamic diameter ranging fromabout 3 to about 5 μm are preferred for delivery to the central andupper airways. Particles having and aerodynamic diameter ranging fromabout 1 to about 3 μm are preferred for delivery to the deep lung.

Inertial impaction and gravitational settling of aerosols arepredominant deposition mechanisms in the airways and acini of the lungsduring normal breathing conditions. Edwards, D. A., J. Aerosol Sci., 26:293-317 (1995). The importance of both deposition mechanisms increasesin proportion to the mass of aerosols and not to particle (or envelope)volume. Since the site of aerosol deposition in the lungs is determinedby the mass of the aerosol (at least for particles of mean aerodynamicdiameter greater than approximately 1 μm), diminishing the tap densityby increasing particle surface irregularities and particle porositypermits the delivery of larger particle envelope volumes into the lungs,all other physical parameters being equal.

The low tap density particles have a small aerodynamic diameter incomparison to the actual envelope sphere diameter. The aerodynamicdiameter, d_(aer), is related to the envelope sphere diameter, d (Gonda,I., “Physico-chemical principles in aerosol delivery,” in Topics inPharmaceutical Sciences 1991 (eds. D. J. A. Crommelin and K. K. Midha),pp. 95-117, Stuttgart: Medpharm Scientific Publishers, 1992)), by theformula:d_(aer)=d√{square root over (ρ)}where the envelope mass p is in units of g/cm³. Maximal deposition ofmonodispersed aerosol particles in the alveolar region of the human lung(˜60%) occurs for an aerodynamic diameter of approximately d_(aer)=3 μm.Heyder, J. et al., J. Aerosol Sci., 17: 811-825 (1986). Due to theirsmall envelope mass density, the actual diameter d of aerodynamicallylight particles comprising a monodisperse inhaled powder that willexhibit maximum deep-lung deposition is:d=3/√{square root over (ρ)}μm (where ρ<1 g/cm³);where d is always greater than 3 μm. For example, aerodynamically lightparticles that display an envelope mass density, ρ=0.1 g/cm³, willexhibit a maximum deposition for particles having envelope diameters aslarge as 9.5 μm. The increased particle size diminishes interparticleadhesion forces. Visser, J., Powder Technology, 58: 1-10. Thus, largeparticle size increases efficiency of aerosolization to the deep lungfor particles of low envelope mass density, in addition to contributingto lower phagocytic losses.

The aerodynamic diameter can be calculated to provide for maximumdeposition within the lungs. Previously this was achieved by the use ofvery small particles of less than about five microns in diameter,preferably between about one and about three microns, which are thensubject to phagocytosis. Selection of particles which have a largerdiameter, but which are sufficiently light (hence the characterization“aerodynamically light”), results in an equivalent delivery to thelungs, but the larger size particles are not phagocytosed.

In one embodiment of the invention, the particles include a biologicallyactive (bioactive) compound, for example a therapeutic, prophylactic ordiagnostic agent. Bioactive compounds or agents also are referred toherein as drugs, active agents, or medicaments. The amount of bioactiveagent present in the particles generally ranges between about 0.1%weight and about 100% weight, preferably between about 1.0% weight andabout 100% weight.

Examples of biologically active agents include synthetic inorganic andorganic compounds, proteins, peptides, polypeptides, DNA and RNA nucleicacid sequences having therapeutic, prophylactic or diagnosticactivities. Nucleic acid sequences include genes, antisense moleculeswhich bind to complementary DNA or RNA and inhibit transcription, andribozymes. The agents to be incorporated can have a variety ofbiological activities, such as vasoactive agents, neuroactive agents,hormones, anticoagulants, immunomodulating agents, cytotoxic agents,prophylactic agents, antibiotics, antivirals, antisense, antigens, andantibodies. Compounds with a wide range of molecular weight can be used,for example, between 100 and 500,000 grams or more per mole.

The particles can include a therapeutic agent for local delivery withinthe lung, such as agents for the treatment of asthma, chronicobstructive pulmonary disease (COPD), emphysema, or cystic fibrosis, orfor systemic treatment. For example, genes for the treatment of diseasessuch as cystic fibrosis can be administered, as can beta agonistssteroids, anticholinergics and leukotriene modifiers for asthma. Otherspecific therapeutic agents include, but are not limited to, humangrowth hormone, insulin, calcitonin, gonadotropin-releasing hormone,luteinizing hormone releasing hormone (LHRH), granulocytecolony-stimulating factor (“G-CSF”), parathyroid hormone and PTH-relatedpeptide, somatostatin, testosterone, progesterone, estradiol, nicotine,fentanyl, norethisterone, clonidine, scopolamine, salicylate, cromolynsodium, salmeterol, formeterol, albuterol, epinephrine, L-dopa, anddiazepam, as well as medicaments that primarily target the centralnervous system, kidneys, heart or other organs.

Diagnostic agents include but are not limited to imaging agents whichinclude commercially available agents used in positron emissiontomography (PET), computer assisted tomography (CAT), single photonemission computerized tomography, x-ray, fluoroscopy, and magneticresonance imaging (MRI).

Examples of suitable materials for use as contrast agents in MRI includebut are not limited to the gadolinium chelates currently available, suchas diethylene triamine pentacetic acid (DTPA) and gadopentotatedimeglumine, as well as iron, magnesium, manganese, copper and chromium.

Examples of materials useful for CAT and x-rays include iodine basedmaterials for intravenous administration, such as ionic monomerstypified by diatrizoate and iothalamate, non-ionic monomers such asiopamidol, isohexyl, and ioversol, non-ionic dimers, such as iotrol andiodixanol, and ionic dimers, for example, ioxagalte.

The particles can include additional component(s). Such additionalcomponents may be referred to herein as excipients, and can include, forexample, phospholipids, surfactants, amino acids, and polymers. In apreferred embodiment, the particles include one or more phospholipids,such as, for example, a phosphatidylcholine, phosphatidylethanolamine,phosphatidylglycerol, phosphatidylserine, phosphatidylinositol or acombination thereof. In one embodiment, the phospholipids are endogenousto the lung. Specific examples of phospholipids are shown in Table 10.Combinations of phospholipids can also be employed. TABLE 10Dilaurylolyphosphatidylcholine (C12:0) DLPCDimyristoylphosphatidylcholine (C14:0) DMPCDipalmitoylphosphatidylcholine (C16:0) DPPCDistearoylphosphatidylcholine (C18:0) DSPC Dioleoylphosphatidylcholine(C18:1) DOPC Dilaurylolylphosphatidylglycerol DLPGDimyristoylphosphatidylglycerol DMPG DipalmitoylphosphatidylglycerolDPPG Distearoylphosphatidylglycerol DSPG DioleoylphosphatidylglycerolDOPG Dimyristoyl phosphatidic acid DMPA Dimyristoyl phosphatidic acidDMPA Dipalmitoyl phosphatidic acid DPPA Dipalmitoyl phosphatidic acidDPPA Dimyristoyl phosphatidylethanolamine DMPE Dipalmitoylphosphatidylethanolamine DPPE Dimyristoyl phosphatidylserine DMPSDipalmitoyl phosphatidylserine DPPS Dipalmitoyl sphingomyelin DPSPDistearoyl sphingomyelin DSSP

Charged phospholipids also can be employed. Examples of chargedphospholipids are described in U.S. patent application entitled“Particles for Inhalation Having Sustained Release Properties,”09/752,106 filed on Dec. 29, 2000, and in U.S. patent application Ser.No. 09/752,109 entitled “Particles for Inhalation Having SustainedRelease Properties”, filed on Dec. 29, 2000; the entire contents of bothare incorporated herein by reference.

The phospholipid can be present in the particles in an amount rangingfrom about 5 weight percent (%) to about 95 weight %. Preferably, it canbe present in the particles in an amount ranging from about 20 weight %to about 80 weight %.

The phospholipids or combinations thereof can be selected to impartcontrolled release properties to the spray dried particles produced bythe methods of the invention. Particles having controlled releaseproperties and methods of modulating release of a biologically activeagent are described in U.S. Provisional Patent Application No.60/150,742 entitled “Modulation of Release From Dry Powder Formulationsby Controlling Matrix Transition,” filed on Aug. 25, 1999 and U.S.Non-Provisional patent application Ser. No. 09/644,736, filed on Aug.23, 2000, with the title “Modulation of Release From Dry PowderFormulations”. The contents of both are incorporated herein by referencein their entirety.

In another embodiment of the invention particles include a surfactant.As used herein, the term “surfactant” refers to any agent whichpreferentially absorbs to an interface between two immiscible phases,such as the interface between water and an organic polymer solution, awater/air interface or organic solvent/air interface. Surfactantsgenerally possess a hydrophilic moiety and a lipophilic moiety, suchthat, upon absorbing to microparticles, they tend to present moieties tothe external environment that do not attract similarly-coated particles,thus reducing particle agglomeration. Surfactants may also promoteabsorption of a therapeutic or diagnostic agent and increasebioavailability of the agent.

In addition to lung surfactants, such as, for example, the phospholipidsdiscussed above, suitable surfactants include but are not limited tohexadecanol; fatty alcohols such as polyethylene glycol (PEG);polyoxyethylene-9-lauryl ether; a surface active fatty acid, such aspalmitic acid or oleic acid; glycocholate; surfactin; a poloxamer; asorbitan fatty acid ester such as sorbitan trioleate (Span 85), Tween 20or Tween 80 (Polyoxyethylene Sorbitan Monooleate); and tyloxapol.

The surfactant can be present in the particles in an amount ranging fromabout 0.01 weight % to about 5 weight %. Preferably, it can be presentin the particles in an amount ranging from about 0.1 weight % to about1.0 weight %.

Methods of preparing and administering particles including surfactants,and, in particular phospholipids, are disclosed in U.S. Pat. No.5,855,913, issued on Jan. 5, 1999 to Hanes et al. and in U.S. Pat. No.5,985,309, issued on Nov. 16, 1999 to Edwards et al. The teachings ofboth are incorporated herein by reference in their entirety.

In another embodiment of the invention, the particles include an aminoacid. Hydrophobic amino acids are preferred. Suitable amino acidsinclude naturally occurring and non-naturally occurring hydrophobicamino acids. Examples of amino acids which can be employed include, butare not limited to: glycine, proline, alanine, cysteine, methionine,valine, leucine, tyrosine, isoleucine, phenylalanine, tryptophan.Preferred hydrophobic amino acids, include but not limited to, leucine,isoleucine, alanine, valine, phenylalanine, glycine and tryptophan.Amino acids which include combinations of hydrophobic amino acids canalso be employed. Non-naturally occurring amino acids include, forexample, beta-amino acids. Both D, L and racemic configurations ofhydrophobic amino acids can be employed. Suitable hydrophobic aminoacids can also include amino acid analogs. As used herein, an amino acidanalog includes the D or L configuration of an amino acid having thefollowing formula: —NH—CHR—CO—, wherein R is an aliphatic group, asubstituted aliphatic group, a benzyl group, a substituted benzyl group,an aromatic group or a substituted aromatic group and wherein R does notcorrespond to the side chain of a naturally-occurring amino acid. Asused herein, aliphatic groups include straight chained, branched orcyclic C1-C8 hydrocarbons which are completely saturated, which containone or two heteroatoms such as nitrogen, oxygen or sulfur and/or whichcontain one or more units of unsaturation. Aromatic groups includecarbocyclic aromatic groups such as phenyl and naphthyl and heterocyclicaromatic groups such as imidazolyl, indolyl, thienyl, furanyl, pyridyl,pyranyl, oxazolyl, benzothienyl, benzofuranyl, quinolinyl, isoquinolinyland acridintyl.

Suitable substituents on an aliphatic, aromatic or benzyl group include—OH, halogen (—Br, —Cl, —I and —F) —O (aliphatic, substituted aliphatic,benzyl, substituted benzyl, aryl or substituted aryl group), —CN, —NO₂,—COOH, —NH2, —NH(aliphatic group, substituted aliphatic, benzyl,substituted benzyl, aryl or substituted aryl group), —N(aliphatic group,substituted aliphatic, benzyl, substituted benzyl, aryl or substitutedaryl group)2, —COO(aliphatic group, substituted aliphatic, benzyl,substituted benzyl, aryl or substituted aryl group), —CONH2,—CONH(aliphatic, substituted aliphatic group, benzyl, substitutedbenzyl, aryl or substituted aryl group)), —SH, —S(aliphatic, substitutedaliphatic, benzyl, substituted benzyl, aromatic or substituted aromaticgroup) and —NH—C(═NH)—NH2. A substituted benzylic or aromatic group canalso have an aliphatic or substituted aliphatic group as a substituent.A substituted aliphatic group can also have a benzyl, substitutedbenzyl, aryl or substituted aryl group as a substituent. A substitutedaliphatic, substituted aromatic or substituted benzyl group can have oneor more substituents. Modifying an amino acid substituent can increase,for example, the lypophilicity or hydrophobicity of natural amino acidswhich are hydrophilic.

A number of the suitable amino acids, amino acid analogs and saltsthereof can be obtained commercially. Others can be synthesized bymethods known in the art. Synthetic techniques are described, forexample, in Green and Wuts, “Protecting Groups in Organic Synthesis”,John Wiley and Sons, Chapters 5 and 7, 1991.

Hydrophobicity is generally defined with respect to the partition of anamino acid between a nonpolar solvent and water. Hydrophobic amino acidsare those acids which show a preference for the nonpolar solvent.Relative hydrophobicity of amino acids can be expressed on ahydrophobicity scale on which glycine has the value 0.5. On such ascale, amino acids which have a preference for water have values below0.5 and those that have a preference for nonpolar solvents have a valueabove 0.5. As used herein, the term hydrophobic amino acid refers to anamino acid that, on the hydrophobicity scale has a value greater orequal to 0.5, in other words, has a tendency to partition in thenonpolar acid which is at least equal to that of glycine.

Combinations of hydrophobic amino acids can also be employed.Furthermore, combinations of hydrophobic and hydrophilic (preferentiallypartitioning in water) amino acids, where the overall combination ishydrophobic, can also be employed. Combinations of one or more aminoacids and one or more phospholipids or surfactants can also be employed.

The amino acid can be present in the particles in an amount from about 0weight % to about 60 weight %. Preferably, the amino acid can be presentin the particles in an amount ranging from about 5 weight % to about 30weight %. The salt of a hydrophobic amino acid can be present in theliquid feed in an amount from about 0 weight % to about 60 weight %.Preferably, the amino acid salt is present in the liquid feed in anamount ranging from about 5 weight % to about 30 weight %. Methods offorming and delivering particles which include an amino acid aredescribed in U.S. patent application Ser. No. 09/382,959, filed on Aug.25, 1999, entitled “Use of Simple Amino Acids to Form Porous ParticlesDuring Spray Drying” and in U.S. patent application Ser. No. 09/644,320filed on Aug. 23, 2000, entitled “Use of Simple Amino Acids to FormPorous Particles”; the teachings of both are incorporated herein byreference in their entirety.

In another embodiment of the invention, the particles include acarboxylate moiety and a multivalent metal salt. One or morephospholipids also can be included. Such compositions are described inU.S. Provisional Application 60/150,662, filed on Aug. 25, 1999,entitled “Formulation for Spray-Drying Large Porous Particles,” and U.S.patent application Ser. No. 09/644,105 filed on Aug. 23, 2000, entitled“Formulation for Spray-Drying Large Porous Particles”; the teachings ofboth are incorporated herein by reference in their entirety. In apreferred embodiment, the particles include sodium citrate and calciumchloride.

Biocompatible, and preferably biodegradable polymers also can beincluded in the particles. Particles including such polymeric materialsare described in U.S. Pat. No. 5,874,064, issued on Feb. 23, 1999 toEdwards et al., the teachings of which are incorporated herein byreference in their entirety, and in U.S. Pat. No. 6,136,295, issued onOct. 24, 2000 to Edwards et al., the entire teachings of which areincorporated herein by reference.

The particles can also include a material such as, for example, dextran,polysaccharides, lactose, trehalose, cyclodextrins, proteins, peptides,polypeptides, fatty acids, inorganic compounds, phosphates.

The total concentration of solids in the liquid feed from which theparticles are formed ranges from about 0.1% to about 0.5% and higher.Solids can include biologically active agent, excipient, phospholipid,surfactants, salts, buffers, metals, and other compounds.

Particles produced by the methods of the invention and which include amedicament, for example one or more of the bioactive agents describedabove, can be administered to the respiratory tract of a patient in needof treatment, prophylaxis or diagnosis. Administration of particles tothe respiratory system can be by means known in the art. For example,particles are delivered from an inhalation device. In a preferredembodiment, particles are administered via a dry powder inhaler (DPI).Metered-dose-inhalers (MDI), or instillation techniques, also can beemployed.

Various suitable devices and methods of inhalation which can be used toadminister particles to a patient's respiratory tract are known in theart. For example, suitable inhalers are described in U.S. Pat. No.4,069,819, issued Aug. 5, 1976 to Valentini, et al., U.S. Pat. No.4,995,385 issued Feb. 26, 1991 to Valentini, et al., and U.S. Pat. No.5,997,848 issued Dec. 7, 1999 to Patton, et al. Other examples ofsuitable inhalers include, but are not limited to, the Spinhaler®(Fisons, Loughborough, U.K.), Rotahaler® (Glaxo-Wellcome, ResearchTriangle Technology Park, North Carolina), FlowCaps® (Hovione, Loures,Portugal), Inhalator® (Boehringer-Ingelheim, Germany), and theAerolizer® (Novartis, Switzerland), the Diskhaler® (Glaxo-Wellcome, RTP,NC) and others known to those skilled in the art. Yet other examples ofsuitable inhalers include those disclosed in the following United Statespatent applications: “Inhalation Device and Method,” application Ser.No. 09/835,302 (filed Apr. 16, 2001) and “Inhalation Device and Method,”application Ser. No. 10/268,059 (filed Oct. 10, 2002), the entirety ofeach of which is incorporated herein by reference.

Preferably, particles administered to the respiratory tract travelthrough the upper airways (oropharynx and larynx), the lower airwayswhich include the trachea followed by bifurcations into the bronchi andbronchioli and through the terminal bronchioli which in turn divide intorespiratory bronchioli leading then to the ultimate respiratory zone,the alveoli or the deep lung. In a preferred embodiment of theinvention, most of the mass of particles deposits in the deep lung. Inanother embodiment of the invention, delivery is primarily to thecentral airways. Delivery to the upper airways can also be obtained.

In one embodiment of the invention, delivery to the pulmonary system ofparticles is in a single, breath-actuated step, as described in U.S.Non-Provisional Patent Application, “High Efficient Delivery of a LargeTherapeutic Mass Aerosol”, application Ser. No. 09/591,307, filed Jun.9, 2000, which is incorporated herein by reference in its entirety. Inanother embodiment of the invention, at least 50% of the mass of theparticles stored in the inhaler receptacle is delivered to a subject'srespiratory system in a single, breath-activated step. In a furtherembodiment, at least 5 milligrams and preferably at least 10 milligramsof a medicament is delivered by administering, in a single breath, to asubject's respiratory tract particles enclosed in the receptacle.Amounts as high as 15, 20, 25, 30, 35, 40 and 50 milligrams can bedelivered.

As used herein, the term “effective amount” means the amount needed toachieve the desired therapeutic or diagnostic effect or efficacy. Theactual effective amounts of drug can vary according to the specific drugor combination thereof being utilized, the particular compositionformulated, the mode of administration, and the age, weight, conditionof the patient, and severity of the symptoms or condition being treated.Dosages for a particular patient can be determined by one of ordinaryskill in the art using conventional considerations, (e.g. by means of anappropriate, conventional pharmacological protocol). In one example,effective amounts of albuterol sulfate range from about 100 micrograms(μg) to about 1.0 milligram (mg).

Aerosol dosage, formulations and delivery systems also may be selectedfor a particular therapeutic application, as described, for example, inGonda, I. “Aerosols for delivery of therapeutic and diagnostic agents tothe respiratory tract,” in Critical Reviews in Therapeutic Drug CarrierSystems, 6: 273-313, 1990; and in Moren, “Aerosol dosage forms andformulations,” in: Aerosols in Medicine. Principles, Diagnosis andTherapy, Moren, et al., Eds, Esevier, Amsterdam, 1985.

The particles of the invention can be employed in compositions suitablefor drug delivery to the pulmonary system. For example, suchcompositions can include the particles and a pharmaceutically acceptablecarrier for administration to a patient, preferably for administrationvia inhalation. The particles may be administered alone or in anyappropriate pharmaceutically acceptable carrier, such as a liquid, forexample saline, or a powder, for administration to the respiratorysystem. They can be co-delivered with larger carrier particles, notincluding a therapeutic agent, the latter possessing mass mediandiameters for example in the range between about 50 μm and about 100 μm.

The present invention will be further understood by reference to thefollowing non-limiting examples.

Examples Preparation of Dry Particles Containing hGH

In a preferred aspect of the present invention, it was desired toprepare inhalable dry particles containing hGH (human growth hormone)that would maximize the amount of active hGH that reached the alveolarspace. To do so, it was determined that the inhalable dry particlesshould have a FPF(5.6) of at least about 85% and a FPF(3.4) of at leastabout 55%. It was also desired to have at least 95% of the hGH in thedry particles be “readily extractable”, that is, soluble in buffersolution. When the hGH is exposed to incompatible components, forexample, organic solutions such as ethanol solution, the hGH degrades ordenatures, resulting in degradation products that include insolubleaggregates and soluble dimer. The method and apparatus of the presentinvention were developed to minimize the amount of insoluble aggregatesand soluble dimer in the finished dry particles by minimizing thecontact between the hGH solution and the incompatible ethanol solutionby combining them rapidly in a static mixer.

The following examples illustrate preparation of inhalable dry particlescontaining hGH. Unless indicated otherwise, bulk raw hGH was supplied byEli Lilly, Inc. as lyophilized powder. 1,2Dipalmitoyl-sn-Glycero-3-Phosphocholine (DPPC) was obtained from AvantiPolar Lipids. USP grade 200 proof ethyl alcohol and USP (United StatesPharmacopeia) Sterile Water for Irrigation were used.

56.1 wt % hGH/40.6 wt % DPPC/3.3 wt % sodium phosphate

The dry particles were prepared in accordance with the followingprocedure, using equipment substantially the same as that illustrated inFIG. 2. The lyophilized hGH powder was allowed to warm to roomtemperature for at least hour. The hGH was dissolved in 1.7 mM sodiumphosphate buffer (pH 7.4) to form a concentrated hGH solution. The pH ofthe hGH concentrate was increased to 7.4 using 1.0 N NaOH. The hGHconcentrate was passed through a Millipore 0.22 μm Opticap filter. Theconcentration of the hGH concentrate was determined using a Beckman Du®640 spectrophotometer. The hGH concentrate solution was diluted with 1.7mM sodium phosphate buffer (pH 7.4) to achieve an hGH concentration of3.57 g/Kg. The resulting aqueous solution was transferred to a sealedvessel, such as feed vessel 210. The organic solution was prepared bydissolving the DPPC in 200 proof ethyl alcohol to a concentration of1.40 g/Kg. The organic solution was transferred into a sealed vessel,such as feed vessel 220.

The aqueous phase was pumped at 15 ml/min±3 ml/min, and the organicphase was pumped at 35 ml/min±3 ml/min into a twelve inch long staticmixer, such as static mixer 230. The combination liquid flowed from thestatic mixer into a rotary atomizer (such as atomizer 240) using a 24vaned rotary atomizer wheel (Niro) operating at 34,500 rpm±2000 rpm. Thecombination was atomized into small droplets, which entered the NiroSize 1 spray dryer (such as spray dryer 250) utilizing dry nitrogen gasflowing at 105 Kg/hr±4 Kg/hr. The inlet temperature of the spray dryerwas maintained at 88° C.±5° C. such that the outlet temperature fellwithin the range of 45° C.±2° C. The particles were collected in a baghouse, such as bag house 260. The resulting dry particles had a meanMMAD of 2.52 μm and a mean VMGD of 10.20 μm.

Size-exclusion HPLC was used to detect and quantitate aggregateformation in the resulting dry particles. As described in more detailbelow, samples were dissolved in 25 mM sodium phosphate buffer, pH 7.0,and in 67% 25 mM sodium phosphate buffer, pH 7.0, containing 33%n-propanol, and filtered through 0.45 μm syringe filters prior tochromatography. Using this technique, hGH elutes as monomer (main peak)at a retention time of 12 to 17 minutes. The appearance of a leadingshoulder on the monomer main peak indicates the presence of solubledimer. The amount of soluble dimer and soluble monomer can be obtainedby determining their respective peak areas. The amount of insolubleaggregate is calculated from the following formula:Insoluble Aggregate (%)=(1−A/B×Area Correction)×100%

-   -   A=Monomer Peak Area of hGH dry particles dissolved in 25 mM        sodium phosphate buffer.    -   B=Monomer Peak Area of hGH dry particles dissolved in 67% 25 mM        sodium phosphate buffer, pH 7.0 containing 33% n-propanol.    -   Area Correction=1.027 (accounts for the difference of the hGH        standard peak area between injections from 33% n-propanol and        buffer).

Size exclusion HPLC was carried out using a Waters 2690 HPLC systemoperating in isocratic mode with a Waters 2487 UV Detector and a TosohasTSK G3000SW, 10 μm (7.5 mm×300 mm) column. The size exclusion column wasrun at 0.6 ml/min using a 0.063 M sodium phosphate buffer:isopropylalcohol (97:3) mobile phase, at pH 7.0. UV detection was at 214 nm.

An alternative method for determining soluble and insoluble aggregatesin protein such as hGH is described below. This method is performedusing size exclusion HPLC with detection at 214 nm on a Waters 2690system with a Waters 2486 dual wavelength detector. A TSK GEL 3000SW 7.5mm×300 mm column is used for the separation with a 63 mM potassiumphosphate, pH 7.0 containing 3% IPA mobile phase flowing at 0.6 mL/minfor 30 min/run at room temperature. Manual integration is performed toquantify monomer, high molecular weight protein (soluble aggregates) andacid dissolved hGH (insoluble aggregates) areas versus a hGH referencestandard calibration curve.

The procedure is as follows:

-   -   Weigh 20 mg of hGH into a scintillation vial and transfer in 20        ml of diluent (25 mM potassium phosphate). This is approximately        0.8 mg/mL hGH monomer. Gently disperse powder solution.    -   Remove approximately 3 ml and filter into an HPLC vial and        inject 20 μL onto the SE HPLC column. This solution is used to        determine the hGH monomer content and the amount of high        molecular weight protein (soluble aggregates).    -   Remove a further 1 ml and transfer to a centrifuge tube.        (Perform in duplicate.)    -   Centrifuge for 10 minutes at 14,000 rpm. Remove and discard the        supernatant. Wash the pellet to remove soluble hGH with 1 ml of        water, and centrifuge for 10 minutes. Repeat this three times.    -   Following the third washing and removal of the water, centrifuge        the tubes one more time to remove any remaining water. Do not        disrupt the pellet.    -   Reconstitute the pellet with 1 ml of 0.01N HCl, and allow it to        dissolve for 15 minutes.    -   Transfer the solution to a HPLC vial and inject 100 μL onto the        column.

The buffer soluble hGH content is determined from the injection of thefirst solution. The insoluble hGH content is determined from injectionof the second solution in 0.01 N HCl. The percent readily extractablehGH is calculated as buffer soluble hGH divided by total hGH content(soluble plus insoluble hGH).

Three experimental runs were made to determine the effect of time in theincompatible ethanol solution on the integrity of the hGH protein. Fortwo of the experiments, a static mixer was not used. Rather, the aqueousand organic solutions were combined, and the combination was maintainedfor a period of time prior to atomization and spray drying. In the firstexperiment (sample 2 in Table 11 below), the aqueous and the organicsolutions were combined prior to spraying, such that the final volumewas 1.25 L, and the resulting combination was spray dried over a periodof 25 minutes. In the second experiment (sample 1 in Table 11 below),the aqueous and organic solutions were combined prior to spraying, suchthat the final volume was 28 L, and the resulting combination was spraydried over a period of 8 hours (560 minutes). In the third experiment,(sample 3 in Table 11 below), the static mixer was used so that theexposure of the hGH to ethanol was about 6 seconds (0.1 minute). Thetotal batch size for sample 3 was 0.375 L of the aqueous solution and0.875 L of the ethanol solution. TABLE 11 Static Maximum ExposureSoluble Insoluble Sample Mixer Time (minutes) Aggregate Aggregate 1 No560 1.60% 26% 2 No 25 5.40% 14% 3 Yes 0.1 3.90% 9%

All of the samples in Table 11 were prepared under the same conditions,with the exception of the amount of exposure time between the aqueousand ethanol solutions prior to spray drying. As can be seen from theresults in Table 11, the insoluble aggregate of the hGH monomerincreased as a function of exposure time to 70% (v/v) ethanol solution.Use of the static mixer decreased the insoluble aggregates by about 17%.

93.5 wt % hGH/6.5 wt % Sodium Phosphate: 10 g/L Ammonium Bicarbonate; 12g/L Solids

Lipid-free particles with a formulation containing hGH and sodiumphosphate monohydrate were prepared as follows using apparatussubstantially as shown in FIG. 6. The aqueous solution was prepared bypreparing a bulk sodium phosphate solution at 100 mM at pH 7.4 and abulk ammonium bicarbonate solution at 50 g/L. 52 mL of 100 mM sodiumphosphate buffer at pH 7.4 was added to 268 mL of water for irrigation.To this was added 200 mL of the 50 g/L ammonium bicarbonate solution and200 mL of ethanol. The resulting solution was combined in a static mixerwith 280 mL of bulk hGH at 40 g/L in 1.7 mM sodium phosphate buffer atpH=7.4. Solute concentration in the combined solution was 12 g/L. Thecombined solution was spray dried under the following processconditions:

-   -   Inlet temperature ˜74° C.    -   Outlet temperature from the drying drum ˜40° C.    -   Nitrogen drying gas=110 kg/hr    -   Nitrogen atomization gas=64 g/min    -   2 Fluid internal mixing nozzle atomizer    -   Nitrogen atomization pressure ˜90 psi    -   Liquid feed rate=25 ml/min    -   Liquid feed temperature ˜22° C.    -   Pressure in drying chamber=−2.0 in water    -   The resulting particles had a FPF(5.6) of 75%, and a FPF(3.4) of        70%, both measured using a 2-stage ACI. The volume mean        geometric diameter was 8 μm at 1.0 bar. The resulting particles        had a soluble dimer fraction of 1.2% and a readily extractable        hGH fraction of 97.5%.

The combination solution flowing out of the static mixer was fed into atwo-fluid nozzle atomizer located above the spray dryer, such asatomizer 640. The contact between the atomized droplets from theatomizer and the heated nitrogen caused the liquid to evaporate from thedroplets, resulting in dry porous particles. The resulting gas-solidstream was fed to bag filter 680 that retained the resulting dryparticles, and allowed the hot gas stream containing the drying gas(nitrogen), evaporated water, and ethanol to pass. The dry particleswere collected into product collection vessel 682.

In order to obtain dry particles of particular physical and chemicalcharacteristics, in vitro characterization tests can be carried out onthe finished dry particles, and the process parameters adjustedaccordingly, as would be apparent to one skilled in the art. Particlesproduced using the apparatus shown in FIG. 2 had a VMGD of 8.4 μm,FPF(5.6) of 89% to 93%, readily extractable hGH fraction of 95.5%, and asoluble dimer fraction of 3%. Particles containing 93.5 wt % hGH and 6.5wt % sodium phosphate were produced using the apparatus substantially asshown in FIG. 6. In this manner, the desired aerodynamic diameter,geometric diameter, and particle density could be obtained for theseparticles in real-time, during the production process.

80 wt % hGH/14 wt % DPPC/6 wt % Sodium Phosphate; 15 g/L AmmoniumBicarbonate; 6 g/L Solids

Particles with a formulation containing hGH, DPPC, and sodium phosphatewere prepared as follows using apparatus substantially as shown in FIG.6. The aqueous solution was prepared by preparing a bulk sodiumphosphate solution at pH 7.4 and a bulk ammonium bicarbonate solution.280 mg of sodium phosphate monobasic was added to 457 mL of water forirrigation. The pH was adjusted to 7.4 using 1.0 N NaOH. To this wasadded 15 g of ammonium bicarbonate and 200 mL of ethanol. 343 mL of 14g/L hGH bulk solution (4.8 g of hGH in 1.7 mM sodium phosphate buffer atpH 7.4) was added to complete the aqueous solution. 840 mg of DPPC wasadded to 200 mL of ethanol to form the ethanol solution. The aqueoussolution was combined in a static mixer with the ethanol solution usinga flow rate of 24 mL/min for the aqueous solution and a flow rate of 6mL/min for the ethanol solution. Solute concentration in the combinedsolution was 6 g/L. The combined solution was spray dried under thefollowing conditions:

Inlet temperature ˜120° C.

Outlet temperature from the drying drum ˜70° C.

Nitrogen drying gas=110 kg/hr.

Nitrogen atomization gas=40 g/min.

2 fluid internal mixing nozzle atomizer.

Nitrogen atomization pressure ˜65 psi.

Liquid feed rate=30 mL/min (24 mL/min aqueous and 6 mL/min ethanol).

Liquid feed temperature ˜22° C.

Pressure in drying chamber=−2.0 in water.

The resulting particles had a FPF (5.6) of 89%, and a FPF (3.4) of 76%,both measured using a 2-stage ACI. The volume mean geometric diameterwas 7.4 μm at 1.0 bar. The resulting particles had a soluble dimerfraction of 3.5% and a readily extractable hGH fraction of 95.6%.

Through the process of the present invention, the formation of proteinaggregates can be minimized. For example, reduced protein aggregation isachieved through, among other things, using the static mixer andcontrolling the level of ethanol in the ethanol solution.

A comparison of powders produced with either batch or static mixing isshown below in Table 12. All of the lots were produced usingsubstantially the same process materials, and process conditions. Thefive combined lots produced with batch mixing generate a lower level ofhigh molecular weight (HMW) protein (soluble dimer=HMW protein) than isgenerated using a static mixing process (n=4 lots). Batch mixing of thespray-dry solution containing 20% ethanol appears beneficial, as itmight allow time to disrupt hydrophobic interactions between the hGHmolecules, and thus reduce hGH aggregation. When ethanol is added to thediluted hGH aqueous phase via the static mixer, a prolongedethanol-aqueous interface occurs and this results in powders havingsomewhat higher levels of soluble aggregates. This occurs because thehGH in the aqueous phase is exposed to higher than optimal ethanollevels which can cause the hGH to unfold and denature. If a static mixeris used for the mixing process, then the hGH is preferably added as aconcentrate to a diluted ethanol/aqueous phase. This is equivalent toadding the hGH last in batch mixing. This is preferred because iteliminates exposing the hGH to high ethanol levels which can perturb itsprotein structure. The effect of the order of addition on solubleaggregate (dimer) levels as a function of ethanol concentration is shownin FIG. 10. The soluble aggregates level is reduced by adding the hGHlast (right column), until the ethanol concentration exceeds about 20%.TABLE 12 Insoluble Lots N = hGH Monomer HMW Protein Aggregates Mixing 579.6% 3.3% 4.4% batch 4 78.4% 5.0% 5.9% static

Conversely, at higher levels of ethanol (>20%), destabilization of theprotein structure may occur, and static mixing was demonstrated to be abetter method of mixing because it reduces the time of exposure of thehGH to the ethanol phase (Table 13). This results in powders with lowerlevels of insoluble aggregates. It has been demonstrated (data notshown) that the time of exposure of the hGH to the ethanol can affectthe level of soluble aggregate formed in the spray-drying formulationsolution. TABLE 13 Insoluble Lot Number HMW Protein Aggregates Organic,Excipient, Mixing 3-63063 5.4% 14.0% 70%, EtOH, batch 3-10697 3.9% 9.0%70%, EtOH, static

93.5 wt % hGH/6.5 wt % Sodium Phosphate

Lipid-free particles with a formulation containing hGH and sodiumphosphate monohydrate were prepared as follows using an apparatussubstantially as shown in FIG. 6. The aqueous solution was prepared bydissolving 0.78 g sodium phosphate dibasic in 500 mL of Water forIrrigation (WFI). To this was added 11.74 bulk hGH lyophilization powderwith water content of 4.4%. The organic solution was prepared bydissolving 30 g of ammonium bicarbonate in 300 mL of water forirrigation, then combined with 200 mL of ethanol. The aqueous solution,at a pH of about 7 and the organic solution were combined in a staticmixer prior to being introduced to the spray dryer nozzle. Soluteconcentration in the combined solution was 12 g/L. The combined solutionwas spray dried under the following process conditions:

Inlet temperature ˜74° C.

Outlet temperature from the drying drum ˜40° C.

Nitrogen drying gas=110 kg/hr

Nitrogen atomization gas=80 g/min

2 Fluid internal mixing nozzle atomizer

Nitrogen atomization back pressure ˜100 psi

Liquid feed rate=25 ml/min

Liquid feed temperature ˜22° C.

Pressure in drying chamber=−2.0 in water

The resulting particles had a FPF(3.3) of 69%, measured using a 3-stagewetted screen ACI. The volume mean geometric diameter was 7.0 μm at 1.0bar. The resulting particles had a HMWP of 1.5% and a readilyextractable hGH fraction of 96%.

The combination solution flowing out of the static mixer was fed into atwo-fluid nozzle atomizer located above the spray dryer, such asatomizer 640. The contact between the atomized droplets from theatomizer and the heated nitrogen caused the liquid to evaporate from thedroplets, resulting in dry porous particles. The resulting gas-solidstream was fed to bag filter 680 that retained the resulting dryparticles, and allowed the hot gas stream containing the drying gas(nitrogen), evaporated water, and ethanol to pass. The dry particleswere collected into product collection vessel 682.

In order to obtain dry particles of particular physical and chemicalcharacteristics, in vitro characterization tests can be carried out onthe finished dry particles, and the process parameters adjustedaccordingly, as would be apparent to one skilled in the art. Particlescontaining 93.5 wt % hGH and 6.5 wt % sodium phosphate were producedusing the apparatus substantially as shown in FIG. 6. In this manner,the desired aerodynamic diameter, geometric diameter, and particledensity could be obtained for these particles in real-time, during theproduction process.

The apparatus and method of the present invention may be adjusted in avariety of ways, including but not limited to those described in thisexample, in order to adjust powder characteristics. For example,lipid-free particles with a formulation containing hGH and sodiumphosphate monohydrate were prepared as prescribed in Tables 14, 15, and16, using an apparatus substantially as shown in FIG. 6. The hGH powdersobtained from these methods are characterized in Table 17. TABLE 14FORMULATIONS USED Sheeting Single-hole Six-hole Action PressureComposition Nozzle Nozzle Nozzle Nozzle hGH concentration, 93.5 93.593.5 93.5 wt. % Sodium phosphate 6.5 6.5 6.5 6.5 concentration, wt. %Tween concen-   0-11.2  0-0.1 0 0 tration, wt. % Solids concen- 6-306-60 15 5-12 tration, g/L Ammonium 0-30 0-40 30-40 30 Bicarbonateconcentration, g/L Overall ethanol 20 20 20 20 concentration, vol. %Overall WFI 80 80 80 80 concentration, vol. % Concentration of 60-70  6060 60 WFI in organic phase, vol. %

TABLE 15 SOLUTION PREPARATION Sheeting Single-hole Six-hole ActionPressure Nozzle Nozzle Nozzle Nozzle Mixer Type Batch and Static StaticStatic Static (Two Solutions) (Two Solutions) (Two Solutions) Order ofSolution Organic Phase: Organic Phase: Organic Phase: Organic Phase:Preparation 1. Amm. Bicarb 1. Amm. Bicarb 1. Amm. Bicarb 1. Amm. Bicarb2. WFI 2. WFI 2. WFI 2. WFI 3. Ethanol 3. Ethanol 3. Ethanol 3. EthanolAqueous Phase: Aqueous Phase: Aqueous Phase: Aqueous Phase: 1. SodiumPhos. 1. Sodium Phos. 1. Sodium Phos. 1. Sodium Phos. 2. WFI 2. WFI 2.WFI 2. WFI 3. hGH 3. hGH 3. hGH 3. hGH Method of Solution Wet and DryWet and Dry Dry Dry Preparation

As indicated in Table 15, “wet” and “dry” methods of solutionpreparation were used. The wet method comprises mixing multiplesolutions (including a concentrated hGH solution and various bufferconcentrations) in order to form the final solutions that are mixed inthe batch or static mixer. This method requires multiple in-processcalculations and mixing many solutions, including a concentrated hGHsolution and various buffer concentrations, to produce the finalsolutions.

The dry method comprises dissolving dry ingredients directly in thefinal solutions that are mixed in the batch or static mixer. The drymethod eliminates in-process calculations and removes the need fordifferent buffer preparations. Instead, the dry method requires initialcalculations of the amount of sodium phosphate dibasic, hGHlyophilization powder and water needed to achieve the desired solutionconcentrations, taking into account the moisture content of thebeginning bulk powder. Those amounts are then dissolved in theappropriate solutions. TABLE 16 PROCESS CONDITIONS Sheeting Single-holeSix-hole Action Pressure Nozzle Nozzle Nozzle Nozzle Operating Pressure−2  −2  −2 −2 in Spray Dryer, W.C. Spray Dryer Outlet 35-70  35-65 45-65  50-71 Temperature, ° C. Atomization Gas 38-120 50-120 200-315 N/ARate, g/min. Aqueous Feed Rate,   4-37.5 5-20 5-40 35 mL/min. OrganicFlow Rate, 7.5-37.5 5-20 5-40 35 mL/min. Total Feed Rate, 10-75  10-40 10-80  70 mL/min. Drying Gas Rate, 80-125 110 110 110-120 kg/hr. MassGas to Feed 1.5-11.1 1.4-13.3 4.2-17.5 N/A Ratio

In this example, a spray dryer operating pressure of −2″ water column(“W.C.”) was used. As is apparent to one of skill in the art, otherspray drying pressures (for example, +2″ W.C.) may be used, dependingupon variations in equipment or other production parameters. TABLE 17RANGE OF CHARACTERIZATION RESULTS Sheeting Single-hole Six-hole ActionPressure Nozzle Nozzle Nozzle Nozzle VMGD @1 bar 4.3-17.4  9.0-25.4 9.8-10.6 21.6 FPF <3.3 micron 29-75/49-84 50/66  45-48  0 FPF MethodACI-3 @ ACI-3 @ ACI-3 @ ACI-3 @ 28.3 lpm/60 lpm 28.3 lpm/ 28.3 lpm 28.3lpm 60 lpm Readily  91-96 92.6-98.3 96.6-98.1 98 Extractable HMWP0.9-1.7  0.8-3.4  1.6-2.6  1.6

The single-hole, two-fluid nozzle depicted in FIG. 4B was used in thisexample. Sample parameters used and powder properties obtained in thisexample using the single-hole nozzle are set forth in Tables 18 and 19.TABLE 18 SAMPLE SOLUTION AND PROCESS CONDITIONS FOR SINGLE-HOLE NOZZLEFeed Solution Solids Concentration 12 g/L Ammonium Bicarbonate conc. 30g/L Solvent: Ethanol/Water (vol/vol %) 20/80 Process Feed Rate 25mL/min. Conditions Atomization Gas Rate 80 g/min. Drying Gas Rate 110kg/hr. Spray Dryer Outlet Temperature 40° C.

TABLE 19 SAMPLE POWDER PROPERTIES WITH SINGLE-HOLE NOZZLE VMGD n = 14HMWP RE (1 bar) FPF_(TD) <3.3 μm Method Average 1.5 95.9 6.7 69 ACI-3,AIR1, 60 lpm StDev 0.3 0.8 0.9 4 ACI-3, AIR1, 60 lpm Range 1.1-2.494.4-97.5 5.3-8.1 61-75 ACI-3, AIR1, 60 lpm

The six-hole nozzle depicted in FIG. 4C was also used in this example.The six-hole nozzle generally produced powders with larger geometricsize and lower density than those produced with the single-hole nozzle.The six-hole nozzle can also process higher solids concentrations, whichincreases production rates and helps with readily extractable values.Sample parameters used and powder properties obtained from this exampleusing the six-hole nozzle are set forth in Tables 20 and 21. TABLE 20SAMPLE SOLUTION AND PROCESS CONDITIONS FOR SIX-HOLE NOZZLE Feed SolutionAmmonium Bicarbonate conc. 30 g/L Solvent: Ethanol/Water (vol/vol %)20/80 Process Conditions Atomization Gas Rate 120 g/min. Drying Gas Rate110 kg/hr. Spray Dryer Outlet Temperature 45° C.

TABLE 21 SAMPLE POWDER PROPERTIES WITH SIX-HOLE NOZZLE Solids LiquidConcen- Feed VMGD FPF_(TD) < tration Rate HMWP RE (1 bar) 3.3 μm Method30 10 1.9 97.7 8.2 66 ACI-3, AIR1, 60 lpm 30 20 1.7 97.7 9.3 63 ACI-3,AIR1, 60 lpm 60 10 1.5 97.4 7.3 57 ACI-3, AIR1, 60 lpm 60 20 1.6 97.98.8 58 ACI-3, AIR1, 60 lpm

The sheeting action nozzle depicted in FIG. 4D was also used in thisexample. This nozzle appears to be a gentler nozzle on the protein, asseen in higher readily extractable value. Adjusting the size of thisnozzle can yield higher FPF values and smaller VMGD values. Sampleparameters used and powder properties obtained from this example usingthe nozzle depicted in FIG. 4D are set forth in Tables 22 and 23. TABLE22 SAMPLE SOLUTION AND PROCESS CONDITIONS FOR SHEETING ACTION NOZZLEFeed Solids Concentration 15 g/L Solution Ammonium Bicarbonate conc. 30g/L Solvent: Ethanol/Water (vol/vol %) 20/80 Process Feed Rate 20mL/min. Conditions Atomization Gas Rate 315 g/min. Drying Gas Rate 110kg/hr. Spray Dryer Outlet Temperature 45° C.

TABLE 23 SAMPLE POWDER PROPERTIES WITH SHEETING ACTION NOZZLE VMGD HMWPRE (1 bar) FPF_(TD) <3.3 μm Method 1.7 98.1 10.3 48 ACI-3, Ch H, 28.3lpm

The pressure nozzle depicted in FIG. 4E was also used in this example.The pressure nozzle is less damaging to the chemical integrity of thehGH in the powder because there is no atomizing gas to produce anair-liquid interface. Sample parameters used and powder propertiesobtained from this example using the pressure nozzle are set forth inTables 24 and 25. TABLE 24 SAMPLE SOLUTION AND PROCESS CONDITIONS FORPRESSURE NOZZLE Nozzle Nozzle hole diameter (in.) 0.016 Core no. 206Feed Solids Concentration 12 g/L Solution Ammonium Bicarbonate conc. 30g/L Solvent: Ethanol/Water (vol/vol %) 20/80 Process Feed Rate 68mL/min. Conditions Atomization Gas Rate 315 g/min. Drying Gas Rate 110kg/hr. Spray Dryer Outlet Temperature 70° C.

TABLE 25 SAMPLE POWDER PROPERTIES WITH PRESSURE NOZZLE VMGD HMWP RE (1bar) FPF_(TD) <3.3 μm Method 1.6 98.0 21.6 0 ACI-3, AIR1, 60 lpm

The addition of non-ionic surfactants to solutions containing hGHsignificantly reduces the formation of insoluble aggregates duringexposure to an air/liquid interface. In particular, use of thesurfactant Tween 80 (which is approved for use in a commercialinhalation product for the treatment of asthma (Pulmicort Respules))reduces the amount of insoluble aggregates of hGH in solution. Non-ionicsurfactants, such as Tween 80, preferentially adsorb to air-waterinterfaces and stabilize proteins against aggregate during processing,such as spray drying. However, excessive use of non-ionic surfactantssuch as Tween 80 is not preferred in pulmonary products. The addition oflow levels of Tween 80 (˜0.2-2.8 wt %) to hGH formulations made with thesingle-hole nozzle increased the readily extractable protein product inthe powder to >99%. The addition of 0.1-0.2 wt % Tween 80 had someeffect but did not provide as much protection. A sample of results fromthis example are set forth in Table 26. TABLE 26 Tween 80 RE 0.1 97.10.2 97.1 2.8 99.9 5.6 99.9 11.2 99.9

The solids concentration is the total concentration of hGH plus anynon-volatile excipients used in the formulation solution. Increasingsolids concentration tends to increase readily extractable hGH andpowder production and tends to reduce FPF. The range of solidsconcentration explored for the single-hole nozzle was 2-30 g/L and forthe six-hole nozzle was 6-60 g/L. Representative results from thisexample are set forth in Tables 27 and 28. TABLE 27 Nozzle Solids Conc.HMWP Insoluble Aggregates Single-hole 2 3.5 13.0 Single-hole 3 5.0 6.8Single-hole 5 6.1 2.2

TABLE 28 Solids VMGD FPF_(TD) < FPF_(TD) < Nozzle Conc. HMWP RE (1 bar)3.3 μm 3.4 μm Single-hole 8 3.2 98.2 6.1 82 Single-hole 12 1.8 98.2 7.369 Single-hole 12 1.5 97.7 8.2 77 Single-hole 30 1.1 96.1 6.2 65Six-hole 15 1.2 97.0 12.7 65 Six-hole 60 1.6 97.9 8.8 58

Ammonium bicarbonate is used as a volatile solid in the spray dryingsolution to help achieve desirable physical characteristics in the finalparticles. As the concentration of ammonium bicarbonate increases, FPFand powder dispersibility improve. However, higher levels increase theHMWP and decrease the readily extractable protein product. The range ofammonium bicarbonate concentration explored for the single-hole nozzlewas 0-30 g/L and for the six-hole nozzle was 0-40 g/L. A sample ofresults from this example are set forth in Table 29. TABLE 29 AmmoniumRicarb VMGD FPF_(TD) < FPF_(TD) < Nozzle Conc. HMWP RE (1 bar) 3.3 μm3.4 μm Single-hole 10 1.1 97.9 9.1 69 Single-hole 29 2.0 96.6 7.6 77Single-hole 0 1.2 95.5 12.4 52 Single-hole 30 1.2 95.5 5.6 70

The addition of alcohol as a co-solvent to the aqueous phase inappropriate amounts helps achieve desired physical characteristics andreduces protein aggregation. Too much alcohol content, however, resultsin detrimental structural changes in the protein. There are two alcohollevels that can affect the hGH: overall alcohol content of the solventsystem and alcohol content that the hGH is exposed to upon mixing. Theoptimum overall alcohol content for the combined solvents was found tobe 20/80 (v/v %) ethanol/water. Contact between hGH and highconcentration ethanol was minimized by diluting the ethanol with waterprior to combining it with the aqueous hGH solution. First, the ethanolwas diluted to 40 vol % and mixed with an equal amount of 100% aqueoushGH solution to create a final feed solution of 20 vol % ethanol. Thisprocedure improved the end product. To test the effects of furtherdilution of the organic phase, further tests were conducted lowering theethanol content to 30 vol % and then mixed with the aqueous hGH phase ata ratio of 2:1 organic:aqueous. In both cases, the single-hole nozzlewas used. Representative results from this example are set forth inTable 30. TABLE 30 Water Content in Organic: Organic Aqueous VMGD Phase(vol %) Ratio HMWP RE (1 bar) FPF_(TD) < 3.3 μm Method 60 1:1 1.6 95.46.1 70 ACI-3, AIR1, 60 lpm 70 2:1 1.6 95.9 6.5 68 ACI-3, AIR1, 60 lpm

Spray dryer outlet temperature is the temperature at the outlet of thespray drying drum. As the outlet temperature increases, the HMWP and theFPF increase and the moisture content decreases. The range of spraydryer outlet temperature explored for the single-hole nozzle was 35-70°C. and for the six-hole nozzle was 35-65° C. Sample results from thisexample are set forth in Table 31. TABLE 31 VMGD Nozzle T_(out, sd) HMWPRE (1 bar) FPF_(TD) < 3.3 μm Method Single-hole 40 1.5 97.2 7.1 57ACI-3, Ch H, 28.3 lpm Single-hole 60 2.1 96.3 6.6 65 ACI-3, Ch H, 28.3lpm

Atomization gas rate is the rate of the high-velocity gas that createsthe liquid droplets in two-fluid atomization. The mass gas to liquidratio (atomization gas to liquid feed rate) affects mean droplet size.Increase in the ratio decreases droplet size, which may in turn increaseFPF. Thus, as atomization gas rate increases, the VMGD tends to decreaseas the FPF increases. The range of atomization gas rate explored for thesingle-hole nozzle was 38-120 g/min and for the six-hole nozzle was50-120 g/min. Representative results from this example are set forth inTable 32. TABLE 32 Atomization VMGD FPF_(TD) < FPF_(TD) < Nozzle GasRate HMWP RE (1 bar) 3.3 μm 3.4 μm Single-hole 46 1.2 97.5 9.6 60Single-hole 64 1.1 97.9 9.1 69 Single-hole 64 1.2 97.9 7.9 71Single-hole 80 1.3 98.6 8.1 78 Single-hole 46 1.6 94.0 9.3 54Single-hole 120 2.4 95.3 7.9 58

The liquid feed rate is the rate at which the liquid solutions arepumped into the atomizer and spray dryer. As the feed rates increase,the gas to liquid ratio decreases and thus the VMGD tends to increase asthe FPF decreases. The range of liquid feed rates explored for thesingle-hole nozzle was 10-75 mL/min and for the six-hole nozzle was10-40 mL/min. Representative results from this example are set forth inTable 33. TABLE 33 Liquid VMGD FPF_(TD) < FPF_(TD) < Nozzle Feed RateHMWP RE (1 bar) 3.3 μm 3.4 μm Single-hole 15 2.2 97.3 7.5 77 Single-hole50 1.8 96.6 8.4 66 Six-hole 25 3.4 97.4 10.2 66 Six-hole 40 3.0 97.315.1 43

The drying gas rate is the rate of the heating gas used to dry thedroplets. This rate also controls the residence time within the dryer.The range of drying gas rate explored for the single-hole nozzle was80-125 kg/hr. Sample results from this example are set forth in Table34. TABLE 34 Drying VMGD Nozzle Gas Rate HMWP RE (1 bar) FPF_(TD) < 3.4μm Method Single-hole 80 1.7 97.9 N/A N/A N/A Single-hole 110 2.1 97.8N/A N/A N/A Single-hole 110 2.8 N/A 7.3 71 ACI-2, AIR1, 60 lpmSingle-hole 125 2.4 N/A 8.0 70 ACI-2, AIR1, 60 lpm

As would be apparent to one of skill in the art, other drying gas ratesmay be used, depending upon variations in equipment or other productionparameters (for example, the size of the dryer). In this example a size1 dryer was used. Use of other size dryers may entail approximately thesame liquid feed to drying gas ratio (mL liq/kg gas), which ranged from4.8 to 56.25 mL liq/kg gas in this example.

Preparation of Dry Particles Containing Insulin

Particles with a formulation containing insulin, DPPC, and sodiumcitrate were prepared using apparatus substantially as shown in FIG. 2,and as described above for hGH. The resulting particles contained 60 wt% DPPC, 30 wt % insulin, and 10 wt % sodium citrate. A 1 L totalcombination volume was used, with a total solute concentration of 3 g/Lin 60/40 ethanol/water. The aqueous solution was prepared as follows.630 mg of citric acid monohydrate was added to 1.0 L of USP water toform 1.0 L of 3.0 mM citrate buffer. The pH was adjusted to 2.5 with 1.0N HCl. 900 mg insulin was dissolved in 400 mL of the citrate buffer. ThepH was adjusted to pH 6.7 using 1.0 N NaOH. The organic solution wasprepared by dissolving 1.8 g of DPPC in 600 mL of ethanol. 400 mL ofwater was added to the organic solution for a total volume of 1 L.

The aqueous insulin solution and the organic solution were combined in astatic mixer, such as static mixer 230. The outflow of the static mixerflowed into rotary atomizer 240, and the resulting atomized dropletswere spray dried in spray dryer 250. The resulting 60 wt % DPPC, 30 wt %insulin, and 10 wt % sodium citrate particles were collected from baghouse 260 into a container.

In order to obtain dry particles of particular physical and chemicalcharacteristics, in vitro characterization tests can be carried out onthe finished dry particles, and the process parameters adjustedaccordingly, as would be apparent to one skilled in the art.Alternatively, particles containing 60 wt % DPPC, 30 wt % insulin, and10 wt % sodium citrate could be produced using the apparatussubstantially as shown in FIG. 6. In this manner, the desiredaerodynamic diameter, geometric diameter, and particle density could beobtained for these particles in real-time, during the productionprocess.

Preparation of Dry Particies Containing Humanized Monoclonal IgG1Antibody

Particles with a formulation containing humanized monoclonal IgG1antibody and DPPC were prepared using apparatus substantially as shownin FIG. 2, and as described above for hGH. The resulting particlescontained 80 wt % humanized monoclonal IgG1 antibody and 20 wt % DPPC. A2 L total combination volume was used, with a total solute concentrationof 1.0 g/L in 30/70 ethanol/water. The aqueous solution was prepared asfollows. 25.0 mL of 47.8 mg/mL humanized monoclonal IgG1 antibodysolution was added to 1400 mL of USP water. The organic solution wasprepared by mixing 0.8 g DPPC with 600 mL of ethanol.

The aqueous solution and the organic solution were combined in a staticmixer, such as static mixer 230. The outflow of the static mixer flowedinto rotary atomizer 240, and the resulting atomized droplets were spraydried in spray dryer 250. The resulting particles were collected frombag house 260 into a container.

In order to obtain dry particles of particular physical and chemicalcharacteristics, in vitro characterization tests can be carried out onthe finished dry particles, and the process parameters adjustedaccordingly, as would be apparent to one skilled in the art.Alternatively, particles containing 80 wt % humanized monoclonal IgG1antibody and 20 wt % DPPC could be produced using the apparatussubstantially as shown in FIG. 6. In this manner, the desiredaerodynamic diameter, geometric diameter, and particle density could beobtained for these particles in real-time, during the productionprocess.

Preparation of Dry Particles Containing Epinephrine

Particles with a formulation containing epinephrine and leucine wereprepared using apparatus substantially as shown in FIG. 2, and asdescribed above for hGH. The resulting particles contained 18 wt %epinephrine bitartrate and 82 wt % leucine. An aqueous solution wasprepared as follows: 900 mg epinephrine bitartrate and 4.1 g leucinewere added to 300 mL of USP water and dissolved by stirring.

The 300 mL of aqueous solution and 700 mL of ethanol were combined in astatic mixer, such as static mixer 230. This resulted in spray drying a1.0 liter total combination volume, with a total solute concentration of5.0 g/L in 70/30 ethanol/water. The outflow of the static mixer flowedinto an atomizer, such as rotary atomizer 240, at an atomization rate of19.5 g/min and a feed rate of 65 ml/min. The resulting atomized dropletswere spray dried using dry nitrogen as the drying gas in spray dryer250. The resulting particles were collected from bag house 260 into acontainer.

In order to obtain dry particles of particular physical and chemicalcharacteristics, in vitro characterization tests can be carried out onthe finished dry particles, and the process parameters adjustedaccordingly, as would be apparent to one skilled in the art.Alternatively, particles containing 18 wt % epinephrine and 82 wt %leucine could be produced using the apparatus substantially as shown inFIG. 6. In this manner, the desired aerodynamic diameter, geometricdiameter, and particle density could be obtained for these particles inreal-time, during the production process.

Preparation of Dry Particles Containing Salmeterol Xinafoate

Particles with a formulation containing salmeterol xinafoate, leucine,and DSPC were prepared using apparatus substantially as shown in FIG. 2,and as described above for hGH. The resulting particles contained 74.55wt % DSPC, 24 wt % leucine, and 1.45 wt % salmeterol xinafoate. A 1 Ltotal combination volume was used, with a total solute concentration of1.0 g/L in 70/30 ethanol/water. The aqueous solution was prepared asfollows. 240 mg leucine was dissolved in 300 mL of USP water. Theorganic solution was prepared by dissolving 745.5 mg DSPC in 700 mL ofethanol. 14.5 mg salmeterol xinafoate was dissolved in the DSPC/ethanolsolution. Both solutions were separately heated to 50° C.

The aqueous solution and the organic solution were combined in a staticmixer, such as static mixer 230. The outflow of the static mixer flowedinto rotary atomizer 240, and the resulting atomized droplets were spraydried in spray dryer 250. The resulting particles were collected frombag house 260 into a container.

In order to obtain dry particles of particular physical and chemicalcharacteristics, in vitro characterization tests can be carried out onthe finished dry particles, and the process parameters adjustedaccordingly, as would be apparent to one skilled in the art.Alternatively, particles containing 74.55 wt % DSPC, 24 wt % leucine,and 1.45 wt % salmeterol xinafoate could be produced using the apparatussubstantially as shown in FIG. 6. In this manner, the desiredaerodynamic diameter, geometric diameter, and particle density could beobtained for these particles in real-time, during the productionprocess.

Preparation of Dry Particles Containing Other Active Agents

Based upon the above examples and description, it would be readilyapparent to one skilled in the art how to prepare dry particlescontaining other active agents using the methods and apparatus of thepresent invention. For example, the apparatus of FIGS. 2 and 6 could beused to prepare dry particles containing a combination of salmeterol andipatroprium bromide in substantially the same manner as described abovefor salmeterol. The apparatus of FIGS. 2 and 6 can also be used, forexample, to prepare dry particles containing albuterol sulfate, DPPC,DSPC, and leucine. The aqueous solution would be prepared by dissolving200 mg leucine in 300 mL water to form an aqueous phase, and dissolving40 mg of albuterol sulfate in the aqueous phase to form the aqueoussolution. The organic solution would be prepared by dissolving 380 mgDPPC in 700 mL of ethanol to form an organic phase, and dissolving 380mg DSPC in the organic phase to form the organic solution. The aqueoussolution and the organic solution would be heated separately to 50° C.The aqueous solution and the organic solution would be combined in astatic mixer, such as static mixer 230. The outflow of the static mixerwould flow into rotary atomizer 240, and the resulting atomized dropletswould be spray dried in spray dryer 250. The resulting particles wouldbe collected from bag house 260 into a container. The resultingparticles would contain 38 wt % DPPC, 38 wt % DSPC, 20 wt % leucine, and4 wt % albuterol sulfate.

CONCLUSION

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. The present invention is not limitedto the preparation of dry particles for inhalation, nor is it limited toa particular active agent, excipient, or solvent, nor is the presentinvention limited to a particular scale, batch size or particle size.Thus, the breadth and scope of the present invention should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the following claims and theirequivalents.

1. A method for preparing a dry powder composition, comprising:combining a first fluid component and a second fluid component in astatic mixer to form a mixed fluid solution, wherein the first fluidcomponent comprises a protein that is incompatible with the second fluidcomponent; atomizing the mixed fluid solution flowing out of the staticmixer to produce droplets, wherein the atomizing step is carried outusing an atomizer that comprises an internal mixing nozzle; and dryingthe droplets in a dryer to form dry particles, wherein the dry particlescontain less than about 6% of soluble dimer of the protein and have aFine Particle Fraction (FPF (3.3)) in the range of about 57-66.
 2. Themethod of claim 1, wherein the atomizing step is performed immediatelyafter the combining step.
 3. The method of claim 1, wherein the proteinis insulin.
 4. The method of claim 2, wherein the protein is insulin. 5.The method of claim 1, further comprising adding a surfactant to thefirst fluid component, the second fluid component, or the mixed fluidsolution.
 6. The method of claim 3, further comprising: adding DPPC tothe first fluid component, the second fluid component, or the mixedfluid solution.
 7. The method of claim 1, wherein the nozzle is asix-hole nozzle.
 8. The method of claim 3, wherein the nozzle is asix-hole nozzle.
 9. The method of claim 1, wherein a solidsconcentration of the mixed fluid solution is more than about 2 g/L. 10.The method of claim 9, wherein the solids concentration of the mixedfluid solution is more than about 5 g/L.
 11. The method of claim 10,wherein the solids concentration of the mixed fluid solution is lessthan about 60 g/L.
 12. The method of claim 11, wherein the solidsconcentration of the mixed fluid solution is less than about 30 g/L. 13.The method of claim 1, further comprising adding about 5-40 g/L ammoniumbicarbonate to the first fluid component, the second fluid component, orthe mixed fluid solution.
 14. The method of claim 1, wherein the secondfluid component is an organic solution comprising approximately 60-70%water by volume and wherein the mixed fluid solution comprisesapproximately 20% organic phase by volume.
 15. The method of claim 14,wherein the second fluid component is an organic solution comprisingapproximately 60% water by volume and wherein the mixed fluid solutioncomprises approximately 20% organic phase by volume.
 16. The method ofclaim 1, wherein the drying step is performed in a dryer with an outlettemperature of 35-70° C.
 17. The method of claim 16, wherein the outlettemperature is approximately 45° C.
 18. The method of claim 1, furthercomprising: ascertaining an amount of solid ingredients necessary toachieve a solution concentration; ascertaining an amount of liquidingredients necessary to achieve the solution concentration; combiningthe liquid ingredients and the solid ingredients to form the first fluidcomponent.
 19. The method of claim 1, wherein the atomizing stepcomprises using an atomization gas rate of approximately 35-120 g/min.20. The method of claim 19, wherein the atomization gas rate isapproximately 120 g/min.
 21. The method of claim 1, wherein theatomizing step comprises using a liquid feed rate of approximately 10-75mL/min.
 22. The method of claim 21, wherein the liquid feed rate isapproximately 10-20 mL/min.
 23. The method of claim 1, wherein thedrying step is performed using a drying gas rate of approximately 80-125kg/hr.
 24. The method of claim 1, wherein the drying gas rate isapproximately 110 kg/hr.